diff --git a/core/modules/block/css/block.admin.css b/core/modules/block/css/block.admin.css
index 407c7c0..0106e83 100644
--- a/core/modules/block/css/block.admin.css
+++ b/core/modules/block/css/block.admin.css
@@ -71,9 +71,9 @@ screen and (min-width: 780px),
 (orientation: landscape) and (min-device-height: 780px) {
 
   .block-list-primary {
-    float: left; /* LTR */
+    float: right; /* LTR */
     width: 75%;
-    padding-right: 2em;
+    padding-left: 2em;
   }
   [dir="rtl"] .block-list-primary {
     float: right;
@@ -82,7 +82,7 @@ screen and (min-width: 780px),
   }
 
   .block-list-secondary {
-    float: right; /* LTR */
+    float: left; /* LTR */
     width: 25%;
   }
   [dir="rtl"] .block-list-secondary {
diff --git a/core/modules/block/lib/Drupal/block/BlockListController.php b/core/modules/block/lib/Drupal/block/BlockListController.php
index da7cbaa..3543106 100644
--- a/core/modules/block/lib/Drupal/block/BlockListController.php
+++ b/core/modules/block/lib/Drupal/block/BlockListController.php
@@ -347,6 +347,7 @@ public function buildForm(array $form, array &$form_state) {
         $form['place_blocks']['list'][$category_key] = array(
           '#type' => 'details',
           '#title' => $category,
+          '#collapsed' => TRUE,
           'content' => array(
             '#theme' => 'links',
             '#links' => array(),
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
index 873d192..a34d9d5 100644
--- a/core/modules/block/templates/block-list.html.twig
+++ b/core/modules/block/templates/block-list.html.twig
@@ -15,10 +15,10 @@
 #}
 {% hide(form.place_blocks) %}
 <div class="layout-block-list clearfix">
-  <div class="layout-region block-list-primary">
-    {{ form }}
-  </div>
   <div class="layout-region block-list-secondary">
     {{ form.place_blocks }}
   </div>
+  <div class="layout-region block-list-primary">
+    {{ form }}
+  </div>
 </div>