diff --git a/features/apply.feature b/features/apply.feature
index 2ec9e427..02219ae6 100644
--- a/features/apply.feature
+++ b/features/apply.feature
@@ -4,11 +4,10 @@ Feature: Apply command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
-          myapp_web:
-            template: myapp_web.rb
+        myapp_vpc:
+          template: myapp_vpc.rb
+        myapp_web:
+          template: myapp_web.rb
       """
     And a directory named "parameters"
     And a file named "parameters/myapp_vpc.yml" with:
@@ -332,12 +331,11 @@ Feature: Apply command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
-            notification_arns:
-              - test_arn
-            stack_policy_file: no_rds_replacement.json
+        myapp_vpc:
+          template: myapp_vpc.rb
+          notification_arns:
+            - test_arn
+          stack_policy_file: no_rds_replacement.json
       """
     And a file named "policies/no_rds_replacement.json" with:
       """
diff --git a/features/apply_with_compile_time_parameters.feature b/features/apply_with_compile_time_parameters.feature
index 3e71823e..0c573b8a 100644
--- a/features/apply_with_compile_time_parameters.feature
+++ b/features/apply_with_compile_time_parameters.feature
@@ -4,9 +4,8 @@ Feature: Apply command with compile time parameters
     Given a file named "stack_master.yml" with:
     """
           stacks:
-            us-east-1:
-              vpc:
-                template: vpc.rb
+            vpc:
+              template: vpc.rb
           """
     And a directory named "parameters"
     And a file named "parameters/vpc.yml" with:
@@ -90,4 +89,4 @@ Feature: Apply command with compile time parameters
       | +      }                                          |
       | +    }                                            |
     And the output should match /2020-10-29 00:00:00 (\+|\-)[0-9]{4} vpc AWS::CloudFormation::Stack CREATE_COMPLETE/
-    Then the exit status should be 0
\ No newline at end of file
+    Then the exit status should be 0
diff --git a/features/apply_with_env_parameters.feature b/features/apply_with_env_parameters.feature
index 921532ef..e930fa62 100644
--- a/features/apply_with_env_parameters.feature
+++ b/features/apply_with_env_parameters.feature
@@ -4,9 +4,8 @@ Feature: Apply command with environment parameter
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us-east-2:
-          vpc:
-            template: vpc.rb
+        vpc:
+          template: vpc.rb
       """
     And a directory named "parameters"
     And a file named "parameters/vpc.yml" with:
@@ -46,4 +45,4 @@ Feature: Apply command with environment parameter
       | +---                  |
       | +VpcCidr: 10.0.0.0/16 |
     And the output should match /2020-10-29 00:00:00 (\+|\-)[0-9]{4} vpc AWS::CloudFormation::Stack CREATE_COMPLETE/
-    Then the exit status should be 0
\ No newline at end of file
+    Then the exit status should be 0
diff --git a/features/apply_with_parameter_store_parameters.feature b/features/apply_with_parameter_store_parameters.feature
index 9eb1f96a..8340b245 100644
--- a/features/apply_with_parameter_store_parameters.feature
+++ b/features/apply_with_parameter_store_parameters.feature
@@ -4,9 +4,8 @@ Feature: Apply command with parameter_store parameter
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us-east-2:
-          vpc:
-            template: vpc.rb
+        vpc:
+          template: vpc.rb
       """
     And a directory named "parameters"
     And a file named "parameters/vpc.yml" with:
diff --git a/features/apply_with_s3.feature b/features/apply_with_s3.feature
index 5f957b25..994d5f70 100644
--- a/features/apply_with_s3.feature
+++ b/features/apply_with_s3.feature
@@ -9,11 +9,10 @@ Feature: Apply command
           region: us-east-1
           prefix: cfn_templates/my-app
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
-            files:
-              - user_data.sh
+        myapp_vpc:
+          template: myapp_vpc.rb
+          files:
+            - user_data.sh
       """
     And a directory named "parameters"
     And a file named "parameters/myapp_vpc.yml" with:
diff --git a/features/diff.feature b/features/diff.feature
index a7c29d0c..1a462a10 100644
--- a/features/diff.feature
+++ b/features/diff.feature
@@ -4,9 +4,8 @@ Feature: Diff command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.json
+        myapp_vpc:
+          template: myapp_vpc.json
       """
     And a directory named "parameters"
     And a file named "parameters/myapp_vpc.yml" with:
diff --git a/features/events.feature b/features/events.feature
index 3f26ddcd..2760f950 100644
--- a/features/events.feature
+++ b/features/events.feature
@@ -4,9 +4,8 @@ Feature: Events command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
+        myapp_vpc:
+          template: myapp_vpc.rb
       """
     And a directory named "templates"
     And a file named "templates/myapp_vpc.rb" with:
diff --git a/features/init.feature b/features/init.feature
index 27fb20e8..45899b52 100644
--- a/features/init.feature
+++ b/features/init.feature
@@ -2,5 +2,4 @@ Feature: init project
 
   Scenario: Run init
     When I run `stack_master init us-east-1 my-app`
-    # TODO flesh this out
     Then the exit status should be 0
diff --git a/features/outputs.feature b/features/outputs.feature
index c4aa3a33..3dec804d 100644
--- a/features/outputs.feature
+++ b/features/outputs.feature
@@ -4,9 +4,8 @@ Feature: Outputs command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
+        myapp_vpc:
+          template: myapp_vpc.rb
       """
     And a directory named "templates"
     And a file named "templates/myapp_vpc.rb" with:
diff --git a/features/region_aliases.feature b/features/region_aliases.feature
index bc789bb6..02a6bec9 100644
--- a/features/region_aliases.feature
+++ b/features/region_aliases.feature
@@ -7,12 +7,8 @@ Feature: Region aliases
         staging: ap-southeast-2
         production: us_east_1
       stacks:
-        staging:
-          myapp_vpc:
-            template: myapp_vpc.rb
-        production:
-          myapp_vpc:
-            template: myapp_vpc.rb
+        myapp_vpc:
+          template: myapp_vpc.rb
       """
     And a directory named "templates"
     And a directory named "parameters"
diff --git a/features/resources.feature b/features/resources.feature
index 113e2664..b5b5a7f1 100644
--- a/features/resources.feature
+++ b/features/resources.feature
@@ -4,9 +4,8 @@ Feature: Resources command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
+        myapp_vpc:
+          template: myapp_vpc.rb
       """
     And a directory named "templates"
     And a file named "templates/myapp_vpc.rb" with:
diff --git a/features/stack_defaults.feature b/features/stack_defaults.feature
index dc9b26ab..25006aff 100644
--- a/features/stack_defaults.feature
+++ b/features/stack_defaults.feature
@@ -21,18 +21,16 @@ Feature: Stack defaults
           tags:
             environment: production
       stacks:
-        ap_southeast_2:
-          myapp_vpc:
-            template: myapp_vpc.rb
-            tags:
-              role: network
-            notification_arns:
-              - test_arn_3
-        us_east_1:
-          myapp_vpc:
-            template: myapp_vpc.rb
-            tags:
-              role: network
+        myapp_vpc:
+          template: myapp_vpc.rb
+          tags:
+            role: network
+          notification_arns:
+            - test_arn_3
+        myotherapp_vpc:
+          template: myapp_vpc.rb
+          tags:
+            role: network
       """
     And a directory named "templates"
     And a directory named "policies"
diff --git a/features/status.feature b/features/status.feature
index 0c307560..797972d1 100644
--- a/features/status.feature
+++ b/features/status.feature
@@ -4,13 +4,12 @@ Feature: Status command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          stack1:
-            template: stack1.json
-          stack2:
-            template: stack2.json
-          stack3:
-            template: stack3.json
+        stack1:
+          template: stack1.json
+        stack2:
+          template: stack2.json
+        stack3:
+          template: stack3.json
       """
     And a directory named "parameters"
     And a file named "parameters/stack1.yml" with:
@@ -106,7 +105,7 @@ Feature: Status command
 }
       """
 
-    When I run `stack_master status --trace`
+    When I run `stack_master status us-east-1 --trace`
     And the output should contain all of these lines:
       | REGION    \| STACK_NAME \| STACK_STATUS    \| DIFFERENT |
       | ----------\|------------\|-----------------\|---------- |
diff --git a/features/validate.feature b/features/validate.feature
index 7da935d7..7f9b12e5 100644
--- a/features/validate.feature
+++ b/features/validate.feature
@@ -4,9 +4,8 @@ Feature: Validate command
     Given a file named "stack_master.yml" with:
       """
       stacks:
-        us_east_1:
-          stack1:
-            template: stack1.json
+        stack1:
+          template: stack1.json
       """
     And a directory named "parameters"
     And a file named "parameters/stack1.yml" with:
diff --git a/lib/stack_master/cli.rb b/lib/stack_master/cli.rb
index c646b4db..71524242 100644
--- a/lib/stack_master/cli.rb
+++ b/lib/stack_master/cli.rb
@@ -115,7 +115,7 @@ def execute!
         c.action do |args, options|
           options.defaults config: default_config_file
           say "Invalid arguments." if args.size > 0
-          config = load_config(options.config)
+          config = load_config(options.config, 'us-east-1')
           StackMaster::Commands::ListStacks.perform(config)
         end
       end
@@ -154,14 +154,13 @@ def execute!
       end
 
       command :status do |c|
-        c.syntax = 'stack_master status'
+        c.syntax = 'stack_master status [region]'
         c.summary = 'Check the current status stacks.'
         c.description = 'Checks the status of all stacks defined in the stack_master.yml file. Warning this operation can be somewhat slow.'
         c.example 'description', 'Check the status of all stack definitions'
         c.action do |args, options|
           options.defaults config: default_config_file
-          say "Invalid arguments. stack_master status" and return unless args.size == 0
-          config = load_config(options.config)
+          config = load_config(options.config, args[0])
           StackMaster::Commands::Status.perform(config)
         end
       end
@@ -180,8 +179,8 @@ def execute!
 
           # Because delete can work without a stack_master.yml
           if options.config and File.file?(options.config)
-            config = load_config(options.config)
-            region = Utils.underscore_to_hyphen(config.unalias_region(args[0]))
+            config = load_config(options.config, args[0])
+            region = config.region
           else
             region = args[0]
           end
@@ -194,9 +193,9 @@ def execute!
       run!
     end
 
-    def load_config(file)
+    def load_config(file, region)
       stack_file = file || default_config_file
-      StackMaster::Config.load!(stack_file)
+      StackMaster::Config.load!(stack_file, region)
     rescue Errno::ENOENT => e
       say "Failed to load config file #{stack_file}"
       exit 1
@@ -204,14 +203,13 @@ def load_config(file)
 
     def execute_stacks_command(command, args, options)
       command_results = []
-      config = load_config(options.config)
+      config = load_config(options.config, args[0])
       args = [nil, nil] if args.size == 0
       args.each_slice(2) do |aliased_region, stack_name|
-        region = Utils.underscore_to_hyphen(config.unalias_region(aliased_region))
         stack_name = Utils.underscore_to_hyphen(stack_name)
-        stack_definitions = config.filter(region, stack_name)
+        stack_definitions = config.filter(stack_name)
         if stack_definitions.empty?
-          StackMaster.stdout.puts "Could not find stack definition #{stack_name} in region #{region}"
+          StackMaster.stdout.puts "Could not find stack definition #{stack_name}"
         end
         stack_definitions = stack_definitions.select do |stack_definition|
           StackStatus.new(config, stack_definition).changed?
diff --git a/lib/stack_master/commands/compile.rb b/lib/stack_master/commands/compile.rb
index caaf79cb..0f94726a 100644
--- a/lib/stack_master/commands/compile.rb
+++ b/lib/stack_master/commands/compile.rb
@@ -16,7 +16,7 @@ def perform
       private
 
       def stack_definition
-        @stack_definition ||= @config.find_stack(@region, @stack_name)
+        @stack_definition ||= @config.find_stack(@stack_name)
       end
 
       def proposed_stack
diff --git a/lib/stack_master/commands/diff.rb b/lib/stack_master/commands/diff.rb
index 48bd4827..668814d7 100644
--- a/lib/stack_master/commands/diff.rb
+++ b/lib/stack_master/commands/diff.rb
@@ -16,7 +16,7 @@ def perform
       private
 
       def stack_definition
-        @stack_definition ||= @config.find_stack(@region, @stack_name)
+        @stack_definition ||= @config.find_stack(@stack_name)
       end
 
       def stack
diff --git a/lib/stack_master/commands/lint.rb b/lib/stack_master/commands/lint.rb
index 0ab868ea..74621491 100644
--- a/lib/stack_master/commands/lint.rb
+++ b/lib/stack_master/commands/lint.rb
@@ -27,7 +27,7 @@ def perform
       private
 
       def stack_definition
-        @stack_definition ||= @config.find_stack(@region, @stack_name)
+        @stack_definition ||= @config.find_stack(@stack_name)
       end
 
       def proposed_stack
diff --git a/lib/stack_master/config.rb b/lib/stack_master/config.rb
index 5e46eda2..c18516c4 100644
--- a/lib/stack_master/config.rb
+++ b/lib/stack_master/config.rb
@@ -5,11 +5,11 @@ module StackMaster
   class Config
     ConfigParseError = Class.new(StandardError)
 
-    def self.load!(config_file = 'stack_master.yml')
+    def self.load!(config_file = 'stack_master.yml', region)
       resolved_config_file = search_up_and_chdir(config_file)
       config = YAML.load(File.read(resolved_config_file))
       base_dir = File.dirname(File.expand_path(resolved_config_file))
-      new(config, base_dir)
+      new(config, base_dir, region)
     rescue Psych::SyntaxError => error
       raise ConfigParseError, "Unable to parse #{resolved_config_file}: #{error}"
     end
@@ -21,6 +21,7 @@ def self.load!(config_file = 'stack_master.yml')
                   :region_defaults,
                   :region_aliases,
                   :template_compilers,
+                  :region,
 
     def self.search_up_and_chdir(config_file)
       return config_file unless File.dirname(config_file) == "."
@@ -35,7 +36,7 @@ def self.search_up_and_chdir(config_file)
       File.join(dir, config_file)
     end
 
-    def initialize(config, base_dir)
+    def initialize(config, base_dir, unaliased_region)
       @config = config
       @base_dir = base_dir
       @template_dir = config.fetch('template_dir', nil)
@@ -46,21 +47,22 @@ def initialize(config, base_dir)
         hash[value] << key
         hash
       end
+      @region = unalias_region(unaliased_region)
       @region_defaults = normalise_region_defaults(config.fetch('region_defaults', {}))
       @stacks = []
       load_template_compilers(config)
       load_config
     end
 
-    def filter(region = nil, stack_name = nil)
+    def filter(stack_name = nil)
       @stacks.select do |s|
-        (region.blank? || s.region == region || s.region == region.gsub('_', '-')) &&
+        (@region.blank? || s.region == @region || s.region == @region.gsub('_', '-')) &&
           (stack_name.blank? || s.stack_name == stack_name || s.stack_name == stack_name.gsub('_', '-'))
       end
     end
 
-    def find_stack(region, stack_name)
-      filter(region, stack_name).first
+    def find_stack(stack_name)
+      filter(stack_name).first
     end
 
     def unalias_region(region)
@@ -94,24 +96,14 @@ def default_template_compilers
     end
 
     def load_config
-      unaliased_stacks = resolve_region_aliases(@config.fetch('stacks'))
-      load_stacks(unaliased_stacks)
-    end
-
-    def resolve_region_aliases(stacks)
-      stacks.inject({}) do |hash, (region, attributes)|
-        hash[unalias_region(region)] = attributes
-        hash
-      end
+      load_stacks(@config.fetch('stacks'))
     end
 
     def load_stacks(stacks)
-      stacks.each do |region, stacks_for_region|
-        region = Utils.underscore_to_hyphen(region)
-        stacks_for_region.each do |stack_name, attributes|
+      stacks.each do |stack_name, attributes|
           stack_name = Utils.underscore_to_hyphen(stack_name)
-          stack_attributes = build_stack_defaults(region).deeper_merge!(attributes).merge(
-            'region' => region,
+        stack_attributes = build_stack_defaults(@region).deeper_merge!(attributes).merge(
+          'region' => @region,
             'stack_name' => stack_name,
             'base_dir' => @base_dir,
             'template_dir' => @template_dir,
@@ -119,7 +111,6 @@ def load_stacks(stacks)
           @stacks << StackDefinition.new(stack_attributes)
         end
       end
-    end
 
     def build_stack_defaults(region)
       region_defaults = @region_defaults.fetch(region, {}).deep_dup
diff --git a/lib/stack_master/utils.rb b/lib/stack_master/utils.rb
index 2149bee6..b40ae132 100644
--- a/lib/stack_master/utils.rb
+++ b/lib/stack_master/utils.rb
@@ -22,9 +22,9 @@ def change_extension(file_name, extension)
     end
 
     def hash_to_aws_parameters(params)
-      params.inject([]) do |params, (key, value)|
-        params << { parameter_key: key, parameter_value: value }
-        params
+      params.inject([]) do |aws_params, (key, value)|
+        aws_params << { parameter_key: key, parameter_value: value }
+        aws_params
       end
     end
 
@@ -41,9 +41,9 @@ def underscore_to_hyphen(string)
     end
 
     def underscore_keys_to_hyphen(hash)
-      hash.inject({}) do |hash, (key, value)|
-        hash[underscore_to_hyphen(key)] = value
-        hash
+      hash.inject({}) do |hash_with_underscore_keys, (key, value)|
+        hash_with_underscore_keys[underscore_to_hyphen(key)] = value
+        hash_with_underscore_keys
       end
     end
   end
diff --git a/spec/fixtures/stack_master.yml b/spec/fixtures/stack_master.yml
index 286a539e..fdf3577a 100644
--- a/spec/fixtures/stack_master.yml
+++ b/spec/fixtures/stack_master.yml
@@ -4,9 +4,6 @@ region_aliases:
 stack_defaults:
   tags:
     application: my-awesome-blog
-  s3:
-    bucket: my-bucket
-    region: us-east-1
 template_compilers:
   rb: ruby_dsl
 region_defaults:
@@ -18,6 +15,9 @@ region_defaults:
     role_arn: test_service_role_arn
     secret_file: production.yml.gpg
     stack_policy_file: my_policy.json
+    s3:
+      bucket: my-bucket
+      region: us-east-1
   staging:
     tags:
       environment: staging
@@ -26,24 +26,25 @@ region_defaults:
       - test_arn_3
     role_arn: test_service_role_arn3
     secret_file: staging.yml.gpg
+    s3:
+      bucket: my-bucket
+      region: ap-southeast-2
 stacks:
-  us-east-1:
-    myapp_vpc:
-      template: myapp_vpc.json
-      notification_arns:
-        - test_arn_2
-      role_arn: test_service_role_arn2
-    myapp_web:
-      template: myapp_web.rb
-    myapp_vpc_with_secrets:
-      template: myapp_vpc.json
-  ap-southeast-2:
-    myapp_vpc:
-      template: myapp_vpc.rb
-      notification_arns:
-        - test_arn_4
-      role_arn: test_service_role_arn4
-    myapp_web:
-      template: myapp_web
-      tags:
-        test_override: 2
+  myapp_vpc:
+    template: myapp_vpc.json
+    notification_arns:
+      - test_arn_2
+    role_arn: test_service_role_arn2
+  myapp_web:
+    template: myapp_web.rb
+  myapp_vpc_with_secrets:
+    template: myapp_vpc.json
+  myotherapp_vpc:
+    template: myapp_vpc.rb
+    notification_arns:
+      - test_arn_4
+    role_arn: test_service_role_arn4
+  myotherapp_web:
+    template: myapp_web
+    tags:
+      test_override: 2
diff --git a/spec/stack_master/config_spec.rb b/spec/stack_master/config_spec.rb
index 0e1e8c40..4a37be36 100644
--- a/spec/stack_master/config_spec.rb
+++ b/spec/stack_master/config_spec.rb
@@ -1,9 +1,10 @@
 RSpec.describe StackMaster::Config do
-  subject(:loaded_config) { StackMaster::Config.load!('spec/fixtures/stack_master.yml') }
+  let(:region) { 'us-east-1' }
+  subject(:loaded_config) { StackMaster::Config.load!('spec/fixtures/stack_master.yml', region) }
   let(:base_dir) { File.expand_path('spec/fixtures') }
   let(:myapp_vpc_definition) {
     StackMaster::StackDefinition.new(
-      region: 'us-east-1',
+      region: region,
       region_alias: 'production',
       stack_name: 'myapp-vpc',
       template: 'myapp_vpc.json',
@@ -48,27 +49,22 @@
 
   describe '#find_stack' do
     it 'returns an object that can find stack definitions' do
-      stack = loaded_config.find_stack('us-east-1', 'myapp-vpc')
+      stack = loaded_config.find_stack('myapp-vpc')
       expect(stack).to eq(myapp_vpc_definition)
     end
 
     it 'can find things with underscores instead of hyphens' do
-      stack = loaded_config.find_stack('us_east_1', 'myapp_vpc')
+      stack = loaded_config.find_stack('myapp_vpc')
       expect(stack).to eq(myapp_vpc_definition)
     end
   end
 
   describe '#filter' do
     it 'returns a list of stack definitions' do
-      stack = loaded_config.filter('us-east-1', 'myapp-vpc')
+      stack = loaded_config.filter('myapp-vpc')
       expect(stack).to eq([myapp_vpc_definition])
     end
 
-    it 'can filter by region only' do
-      stacks = loaded_config.filter('us-east-1')
-      expect(stacks.size).to eq 3
-    end
-
     it 'can return all stack definitions with no filters' do
       stacks = loaded_config.filter
       expect(stacks.size).to eq 5
@@ -82,7 +78,6 @@
   it 'loads stack defaults' do
     expect(loaded_config.stack_defaults).to eq({
       'tags' => { 'application' => 'my-awesome-blog' },
-      's3' => { 'bucket' => 'my-bucket', 'region' => 'us-east-1' }
     })
   end
 
@@ -103,13 +98,15 @@
         'role_arn' => 'test_service_role_arn',
         'notification_arns' => ['test_arn'],
         'secret_file' => 'production.yml.gpg',
-        'stack_policy_file' => 'my_policy.json'
+        'stack_policy_file' => 'my_policy.json',
+        's3' => { 'bucket' => 'my-bucket', 'region' => 'us-east-1'}
       },
       'ap-southeast-2' => {
         'tags' => {'environment' => 'staging', 'test_override' => 1 },
         'role_arn' => 'test_service_role_arn3',
         'notification_arns' => ['test_arn_3'],
-        'secret_file' => 'staging.yml.gpg'
+        'secret_file' => 'staging.yml.gpg',
+        's3' => { 'bucket' => 'my-bucket', 'region' => 'ap-southeast-2' }
       }
     })
   end
@@ -121,45 +118,46 @@
     )
   end
 
-  it 'deep merges stack attributes' do
-    expect(loaded_config.find_stack('ap-southeast-2', 'myapp-vpc')).to eq(StackMaster::StackDefinition.new(
-      stack_name: 'myapp-vpc',
-      region: 'ap-southeast-2',
-      region_alias: 'staging',
-      tags: {
-        'application' => 'my-awesome-blog',
-        'environment' => 'staging',
-        'test_override' => 1
-      },
-      s3: { 'bucket' => 'my-bucket', 'region' => 'us-east-1' },
-      role_arn: 'test_service_role_arn4',
-      notification_arns: ['test_arn_3', 'test_arn_4'],
-      template: 'myapp_vpc.rb',
-      base_dir: base_dir,
-      secret_file: 'staging.yml.gpg',
-      additional_parameter_lookup_dirs: ['staging']
-    ))
-    expect(loaded_config.find_stack('ap-southeast-2', 'myapp-web')).to eq(StackMaster::StackDefinition.new(
-      stack_name: 'myapp-web',
-      region: 'ap-southeast-2',
-      region_alias: 'staging',
-      tags: {
-        'application' => 'my-awesome-blog',
-        'environment' => 'staging',
-        'test_override' => 2
-      },
-      s3: { 'bucket' => 'my-bucket', 'region' => 'us-east-1' },
-      role_arn: 'test_service_role_arn3',
-      notification_arns: ['test_arn_3'],
-      template: 'myapp_web',
-      base_dir: base_dir,
-      secret_file: 'staging.yml.gpg',
-      additional_parameter_lookup_dirs: ['staging']
-    ))
+  context 'in the staging environment' do
+    let(:region) { 'staging' }
+    it 'deep merges stack attributes' do
+      expect(loaded_config.find_stack('myotherapp-vpc')).to eq(StackMaster::StackDefinition.new(
+        stack_name: 'myotherapp-vpc',
+        region: 'ap-southeast-2',
+        tags: {
+          'application' => 'my-awesome-blog',
+          'environment' => 'staging',
+          'test_override' => 1
+        },
+        s3: { 'bucket' => 'my-bucket', 'region' => 'ap-southeast-2' },
+        role_arn: 'test_service_role_arn4',
+        notification_arns: ['test_arn_3', 'test_arn_4'],
+        template: 'myapp_vpc.rb',
+        base_dir: base_dir,
+        secret_file: 'staging.yml.gpg',
+        additional_parameter_lookup_dirs: ['staging']
+      ))
+      expect(loaded_config.find_stack('myotherapp-web')).to eq(StackMaster::StackDefinition.new(
+        stack_name: 'myotherapp-web',
+        region: 'ap-southeast-2',
+        tags: {
+          'application' => 'my-awesome-blog',
+          'environment' => 'staging',
+          'test_override' => 2
+        },
+        s3: { 'bucket' => 'my-bucket', 'region' => 'ap-southeast-2' },
+        role_arn: 'test_service_role_arn3',
+        notification_arns: ['test_arn_3'],
+        template: 'myapp_web',
+        base_dir: base_dir,
+        secret_file: 'staging.yml.gpg',
+        additional_parameter_lookup_dirs: ['staging']
+      ))
+    end
   end
 
   it 'allows region aliases in region defaults' do
-    config = StackMaster::Config.new({'region_aliases' => { 'production' => 'us-east-1' }, 'region_defaults' => { 'production' => { 'secret_file' => 'production.yml.gpg' }}, 'stacks' => {}}, '/base')
+    config = StackMaster::Config.new({'region_aliases' => { 'production' => 'us-east-1' }, 'region_defaults' => { 'production' => { 'secret_file' => 'production.yml.gpg' }}, 'stacks' => {}}, '/base', 'us-east-1')
     expect(config.region_defaults).to eq('us-east-1' => { 'secret_file' => 'production.yml.gpg' })
   end
 end
diff --git a/spec/stack_master/stack_spec.rb b/spec/stack_master/stack_spec.rb
index c26c5226..18ece854 100644
--- a/spec/stack_master/stack_spec.rb
+++ b/spec/stack_master/stack_spec.rb
@@ -75,7 +75,7 @@
   describe '.generate' do
     let(:tags) { {'tag1' => 'value1'} }
     let(:stack_definition) { StackMaster::StackDefinition.new(region: region, stack_name: stack_name, tags: tags, base_dir: '/base_dir', template: template_file_name, notification_arns: ['test_arn'], role_arn: 'test_service_role_arn', stack_policy_file: 'no_replace_rds.json') }
-    let(:config) { StackMaster::Config.new({'stacks' => {}}, '/base_dir') }
+    let(:config) { StackMaster::Config.new({'stacks' => {}}, '/base_dir', region) }
     subject(:stack) { StackMaster::Stack.generate(stack_definition, config) }
     let(:parameter_hash) { {template_parameters: {'DbPassword' => {'secret' => 'db_password'}}, compile_time_parameters: {}} }
     let(:resolved_template_parameters) { {'DbPassword' => 'sdfgjkdhlfjkghdflkjghdflkjg', 'InstanceType' => 't2.medium'} }
diff --git a/spec/stack_master/validator_spec.rb b/spec/stack_master/validator_spec.rb
index 39f78ca8..c9694334 100644
--- a/spec/stack_master/validator_spec.rb
+++ b/spec/stack_master/validator_spec.rb
@@ -1,11 +1,12 @@
 RSpec.describe StackMaster::Validator do
 
   subject(:validator) { described_class.new(stack_definition, config) }
-  let(:config) { StackMaster::Config.new({'stacks' => {}}, '/base_dir') }
+  let(:region) { 'us-east-1' }
+  let(:config) { StackMaster::Config.new({'stacks' => {}}, '/base_dir', region) }
   let(:stack_name) { 'myapp_vpc' }
   let(:stack_definition) do
     StackMaster::StackDefinition.new(
-        region: 'us-east-1',
+        region: region,
         stack_name: stack_name,
         template: 'myapp_vpc.json',
         tags: {'environment' => 'production'},