diff --git a/app/assets/javascripts/sidenav.js b/app/assets/javascripts/sidenav.js
index 289b0a03a..24c9f2c5b 100644
--- a/app/assets/javascripts/sidenav.js
+++ b/app/assets/javascripts/sidenav.js
@@ -1,42 +1,57 @@
 document.addEventListener('DOMContentLoaded', () => {
     const sidenavItems = document.querySelectorAll('.usa-sidenav__item > .parent-link');
+    let lastPath = window.location.pathname;
+    let debounceTimeout = null;
 
     sidenavItems.forEach((link) => {
       const parentItem = link.parentElement;
-      const hasChildren = parentItem.querySelector('.usa-sidenav__sublist');
-      const currentUrl = window.location.pathname;
+      const sublist = parentItem.querySelector('.usa-sidenav__sublist');
+      const targetHref = link.getAttribute('href');
 
-      if (
-        link.getAttribute('href') === currentUrl ||
-        currentUrl.startsWith(link.getAttribute('href'))
-      ) {
+      // initialize the menu to open the correct submenu based on the current route
+      if (window.location.pathname.startsWith(targetHref)) {
         parentItem.classList.add('open');
         link.setAttribute('aria-expanded', 'true');
       }
 
       link.addEventListener('click', (event) => {
-        if (hasChildren) {
-          event.preventDefault();
-
-          const isOpen = parentItem.classList.contains('open');
+        const currentPath = window.location.pathname;
 
-          document.querySelectorAll('.usa-sidenav__item.open').forEach((item) => {
-            if (item !== parentItem) {
-              item.classList.remove('open');
-              item.querySelector('.parent-link').setAttribute('aria-expanded', 'false');
-            }
-          });
+        // prevent default behavior only if navigating to the same route
+        if (currentPath === targetHref) {
+          event.preventDefault();
+          return;
+        }
 
-          if (!isOpen) {
+        if (sublist && !parentItem.classList.contains('open')) {
+          // debounce the menu update to avoid flickering
+          clearTimeout(debounceTimeout);
+          debounceTimeout = setTimeout(() => {
             parentItem.classList.add('open');
             link.setAttribute('aria-expanded', 'true');
-          } else {
-            parentItem.classList.remove('open');
-            link.setAttribute('aria-expanded', 'false');
-          }
+          }, 50);
+        }
+      });
+    });
+
+    // handle browser back/forward navigation
+    window.addEventListener('popstate', () => {
+      const currentPath = window.location.pathname;
 
-          window.location.href = link.getAttribute('href');
+      // sync menu state
+      sidenavItems.forEach((link) => {
+        const parentItem = link.parentElement;
+        const targetHref = link.getAttribute('href');
+
+        if (currentPath.startsWith(targetHref)) {
+          parentItem.classList.add('open');
+          link.setAttribute('aria-expanded', 'true');
+        } else {
+          parentItem.classList.remove('open');
+          link.setAttribute('aria-expanded', 'false');
         }
       });
+
+      lastPath = currentPath;
     });
   });
diff --git a/app/assets/sass/uswds/_uswds-theme-custom-styles.scss b/app/assets/sass/uswds/_uswds-theme-custom-styles.scss
index 59bc5e12f..c06bc43ab 100644
--- a/app/assets/sass/uswds/_uswds-theme-custom-styles.scss
+++ b/app/assets/sass/uswds/_uswds-theme-custom-styles.scss
@@ -915,17 +915,20 @@ li.linked-card:hover svg,
 }
 
 .usa-sidenav__sublist {
-  display: none; /* Default: hidden */
+  display: none;
 }
 
 .usa-sidenav__item.open .usa-sidenav__sublist {
-  display: block; /* Show sublist when the parent has the 'open' class */
+  display: block;
 }
 
 .usa-sidenav__sublist .bold {
   font-weight: bold;
 }
 
+.usa-sidenav__sublist li[role="menuitem"] {
+  border-top: 1px solid #dfe1e2;
+}
 
 .icon-list {
   display: flex;
diff --git a/app/templates/base.html b/app/templates/base.html
index 1d2778a9e..bc46d3171 100644
--- a/app/templates/base.html
+++ b/app/templates/base.html
@@ -50,7 +50,7 @@
           {% block maincolumn_content %}
               <div class="grid-row">
                 {% if navigation_links %}
-                  <div class="tablet:grid-col-2 margin-bottom-4">
+                  <div class="tablet:grid-col-3 margin-bottom-4">
                     <nav class="nav">
                       <ul class="usa-sidenav">
                         {% for item in navigation_links %}
@@ -80,9 +80,9 @@
 
                     </nav>
                   </div>
-                  <div class="tablet:grid-col-10 tablet:padding-left-4 usa-prose site-prose">
+                  <div class="tablet:grid-col-9 tablet:padding-left-4 usa-prose site-prose">
                 {% else %}
-                  <div class="tablet:grid-col-10">
+                  <div class="tablet:grid-col-9">
                 {% endif %}
                 {% block content_column_content %}{% endblock %}
                 </div>
diff --git a/app/templates/components/header.html b/app/templates/components/header.html
index 339e07518..3b86c7725 100644
--- a/app/templates/components/header.html
+++ b/app/templates/components/header.html
@@ -39,7 +39,7 @@
 
 {% if FEATURE_ABOUT_PAGE_ENABLED %}
 {% set navigation = navigation + [
-  {"href": url_for('main.about_notify'), "text": "About Notify", "active": request.path == '/about'},
+  {"href": url_for('main.about_notify'), "text": "About Notify", "active": request.path.startswith('/about')},
   {"href": url_for('main.join_notify'), "text": "Join Notify", "active": request.path == '/join-notify'},
   {"href": url_for('main.contact'), "text": "Contact us", "active": request.path == '/contact'}
 ] %}