diff --git a/internal_packages/message-list/lib/message-list.cjsx b/internal_packages/message-list/lib/message-list.cjsx
index f39089a18..a982bbfe3 100755
--- a/internal_packages/message-list/lib/message-list.cjsx
+++ b/internal_packages/message-list/lib/message-list.cjsx
@@ -8,6 +8,7 @@ MessageItem = require "./message-item"
  DraftStore,
  MessageStore,
  DatabaseStore,
+ WorkspaceStore,
  ComponentRegistry,
  ChangeLabelsTask,
  UpdateThreadsTask} = require("nylas-exports")
@@ -20,6 +21,34 @@ MessageItem = require "./message-item"
  MailLabel,
  InjectedComponent} = require('nylas-component-kit')
 
+class HideSidebarButton extends React.Component
+  constructor: (@props) ->
+    @column = WorkspaceStore.Location.MessageListSidebar
+    @state = @getStateFromStores()
+
+  componentDidMount: =>
+    @unlisten = WorkspaceStore.listen => @setState(@getStateFromStores())
+
+  componentWillUnmount: =>
+    @unlisten()
+
+  render: =>
+    if @state.hidden
+      contents = {label: 'Show Sidebar', name: 'icon-thread-showsidebar.png'}
+    else
+      contents = {label: 'Hide Sidebar', name: 'icon-thread-hidesidebar.png'}
+
+    <div className="hide-sidebar-button" style={@props.style} onClick={@_onClick}>
+      <span className="img-wrap"><RetinaImg name={contents.name} mode={RetinaImg.Mode.ContentIsMask}/></span>
+      {contents.label}
+    </div>
+
+  _onClick: =>
+    Actions.toggleWorkspaceLocationHidden(@column)
+
+  getStateFromStores: =>
+    {hidden: WorkspaceStore.isLocationHidden(@column)}
+
 class MessageListScrollTooltip extends React.Component
   @displayName: 'MessageListScrollTooltip'
   @propTypes:
@@ -226,7 +255,7 @@ class MessageList extends React.Component
 
   _renderSubject: ->
     <div className="message-subject-wrap">
-      <div className="message-count">{@state.messages.length} {if @state.messages.length is 1 then "message" else "messages"}</div>
+      <HideSidebarButton style={float:'right'}/>
       <span className="message-subject">{@state.currentThread?.subject}</span>
       {@_renderLabels()}
     </div>
diff --git a/internal_packages/message-list/stylesheets/message-list.less b/internal_packages/message-list/stylesheets/message-list.less
index 34db31336..8cca9c14f 100644
--- a/internal_packages/message-list/stylesheets/message-list.less
+++ b/internal_packages/message-list/stylesheets/message-list.less
@@ -49,6 +49,19 @@
   }
 }
 
+.hide-sidebar-button {
+  font-size: @font-size-small;
+  color: @text-color-subtle;
+  margin-left: @spacing-standard;
+  cursor:default;
+  .img-wrap {
+    margin-right: @spacing-half;
+    position: relative;
+    top: -1px;
+  }
+  img { background: @text-color-subtle; }
+}
+
 #message-list {
   display: flex;
   flex-direction: column;
@@ -64,7 +77,7 @@
     width: calc(~"100% - 12px");
     max-width: @message-max-width;
     margin: 11px auto 10px auto;
-    padding: 0 20px;
+    padding-left: 20px;
     -webkit-user-select: text;
     line-height: @font-size-large * 1.8;
   }
@@ -73,12 +86,6 @@
     color: @text-color;
     margin-right: @spacing-standard;
   }
-  .message-count {
-    float: right;
-    font-size: @font-size-small;
-    color: @text-color-very-subtle;
-  }
-
   .message-list-headers {
     margin: 0 auto;
     width: 100%;
diff --git a/internal_packages/mode-switch/lib/mode-toggle.cjsx b/internal_packages/mode-switch/lib/mode-toggle.cjsx
index d926b2817..11eceff63 100644
--- a/internal_packages/mode-switch/lib/mode-toggle.cjsx
+++ b/internal_packages/mode-switch/lib/mode-toggle.cjsx
@@ -21,7 +21,7 @@ class ModeToggle extends React.Component
     return <div></div> unless @state.visible
 
     <div className="btn btn-toolbar mode-toggle mode-#{@state.mode}"
-         style={order:51}
+         style={order:500}
          onClick={@_onToggleMode}>
       <RetinaImg
         name="toolbar-icon-toggle-pane.png"
diff --git a/src/components/mail-label.cjsx b/src/components/mail-label.cjsx
index 90d7fdc34..0158096c3 100644
--- a/src/components/mail-label.cjsx
+++ b/src/components/mail-label.cjsx
@@ -1,5 +1,6 @@
 React = require 'react'
 RetinaImg = require './retina-img'
+CategoryStore = require '../flux/stores/category-store'
 
 class MailLabel extends React.Component
   @propTypes:
@@ -18,7 +19,7 @@ class MailLabel extends React.Component
     content = @props.label.displayName
 
     x = null
-    if @props.onRemove
+    if @_removable()
       classname += ' removable'
       content = <span className="inner">{content}</span>
       x = <RetinaImg
@@ -30,6 +31,8 @@ class MailLabel extends React.Component
 
     <div className={classname} style={style}>{content}{x}</div>
 
-  _renderX: ->
+  _removable: ->
+    isLockedLabel = @props.label.name in CategoryStore.LockedCategoryNames
+    return @props.onRemove and not isLockedLabel
 
 module.exports = MailLabel
diff --git a/src/flux/actions.coffee b/src/flux/actions.coffee
index d1d90a91c..c2f8c348d 100644
--- a/src/flux/actions.coffee
+++ b/src/flux/actions.coffee
@@ -175,6 +175,15 @@ class Actions
   ###
   @selectLayoutMode: ActionScopeWindow
 
+  ###
+  Public: Toggle whether a particular column is visible. Call this action
+  with one of the Sheet location constants:
+
+  ```
+  Actions.toggleWorkspaceLocationHidden(WorkspaceStore.Location.MessageListSidebar)
+  ```
+  ###
+  @toggleWorkspaceLocationHidden: ActionScopeWindow
 
   ###
   Public: Focus the keyboard on an item in a collection. This action moves the
diff --git a/src/flux/stores/workspace-store.coffee b/src/flux/stores/workspace-store.coffee
index a1c8ba2dc..dfcab1a9d 100644
--- a/src/flux/stores/workspace-store.coffee
+++ b/src/flux/stores/workspace-store.coffee
@@ -30,6 +30,8 @@ class WorkspaceStore
     @listenTo Actions.selectLayoutMode, @_onSelectLayoutMode
     @listenTo Actions.setFocus, @_onSetFocus
 
+    @listenTo Actions.toggleWorkspaceLocationHidden, @_onToggleLocationHidden
+
     @listenTo Actions.popSheet, @popSheet
     @listenTo Actions.searchQueryCommitted, @popToRootSheet
 
@@ -41,6 +43,7 @@ class WorkspaceStore
     @Sheet = Sheet = {}
 
     @_preferredLayoutMode = 'list'
+    @_hiddenLocations = {}
     @_sheetStack = []
 
     if atom.isMainWindow()
@@ -71,6 +74,16 @@ class WorkspaceStore
     @_preferredLayoutMode = mode
     @trigger(@)
 
+  _onToggleLocationHidden: (location) =>
+    if not location.id
+      throw new Error("Actions.toggleWorkspaceLocationHidden - pass a WorkspaceStore.Location")
+
+    if @_hiddenLocations[location.id]
+      delete @_hiddenLocations[location.id]
+    else
+      @_hiddenLocations[location.id] = location
+    @trigger(@)
+
   _onSetFocus: ({collection, item}) =>
     if collection is 'thread'
       if @layoutMode() is 'list'
@@ -101,22 +114,32 @@ class WorkspaceStore
     else
       root.supportedModes[0]
 
-  # Returns The top {Sheet} in the current stack. Use this method to determine
+  # Public: Returns The top {Sheet} in the current stack. Use this method to determine
   # the sheet the user is looking at.
   #
   topSheet: =>
     @_sheetStack[@_sheetStack.length - 1]
 
-  # Returns The {Sheet} at the root of the current stack.
+  # Public: Returns The {Sheet} at the root of the current stack.
   #
   rootSheet: =>
     @_sheetStack[0]
 
-  # Returns an {Array<Sheet>} The stack of sheets
+  # Public: Returns an {Array<Sheet>} The stack of sheets
   #
   sheetStack: =>
     @_sheetStack
 
+  # Public: Returns an {Array} of locations that have been hidden.
+  #
+  hiddenLocations: =>
+    _.values(@_hiddenLocations)
+
+  # Public: Returns a {Boolean} indicating whether the location provided is hidden.
+  # You should provide one of the WorkspaceStore.Location constant values.
+  isLocationHidden: (loc) =>
+    @_hiddenLocations[loc.id]
+
   ###
   Managing Sheets
   ###
diff --git a/src/sheet-toolbar.cjsx b/src/sheet-toolbar.cjsx
index 35aa70575..67c9a8dfd 100644
--- a/src/sheet-toolbar.cjsx
+++ b/src/sheet-toolbar.cjsx
@@ -182,6 +182,7 @@ class Toolbar extends React.Component
     # Add items registered to Regions in the current sheet
     if @props.data?.columns[state.mode]?
       for loc in @props.data.columns[state.mode]
+        continue if WorkspaceStore.isLocationHidden(loc)
         entries = ComponentRegistry.findComponentsMatching({location: loc.Toolbar, mode: state.mode})
         state.columns.push(entries)
 
diff --git a/src/sheet.cjsx b/src/sheet.cjsx
index 3d5228618..5e2f4e1f0 100644
--- a/src/sheet.cjsx
+++ b/src/sheet.cjsx
@@ -90,6 +90,7 @@ class Sheet extends React.Component
 
     if @props.data?.columns[state.mode]?
       for location, idx in @props.data.columns[state.mode]
+        continue if WorkspaceStore.isLocationHidden(location)
         entries = ComponentRegistry.findComponentsMatching({location: location, mode: state.mode})
         maxWidth = _.reduce entries, ((m,component) -> Math.min(component.containerStyles?.maxWidth ? 10000, m)), 10000
         minWidth = _.reduce entries, ((m,component) -> Math.max(component.containerStyles?.minWidth ? 0, m)), 0
diff --git a/static/images/message-list-toggle-sidebar/icon-thread-hidesidebar@2x.png b/static/images/message-list-toggle-sidebar/icon-thread-hidesidebar@2x.png
new file mode 100644
index 000000000..fa6fc9eb3
Binary files /dev/null and b/static/images/message-list-toggle-sidebar/icon-thread-hidesidebar@2x.png differ
diff --git a/static/images/message-list-toggle-sidebar/icon-thread-showsidebar@2x.png b/static/images/message-list-toggle-sidebar/icon-thread-showsidebar@2x.png
new file mode 100644
index 000000000..8c8330c63
Binary files /dev/null and b/static/images/message-list-toggle-sidebar/icon-thread-showsidebar@2x.png differ
diff --git a/static/workspace.less b/static/workspace.less
index d9fcb3011..2c55b26a3 100644
--- a/static/workspace.less
+++ b/static/workspace.less
@@ -203,14 +203,12 @@ body.is-blurred {
 
   .btn-toolbar {
     margin-top: @spacing-three-quarters;
-    margin-left: @spacing-three-quarters;
     margin-right: @spacing-three-quarters;
+    margin-left: 0;
     flex-shrink: 0;
     height:28px;
   }
-  .btn-toolbar:last-child {
-    margin-left: 0;
-  }
+  .btn-toolbar:first-child ,
   .btn-toolbar:only-child {
     margin-left: @spacing-three-quarters;
   }