diff --git a/templates/zephyr/index.html b/templates/zephyr/index.html
index f91a9d2fe0..c2e3c0bd77 100644
--- a/templates/zephyr/index.html
+++ b/templates/zephyr/index.html
@@ -55,6 +55,7 @@
 <script type="text/javascript" src="{{ static_hidden }}js/composebox_typeahead.js"></script>
 <script type="text/javascript" src="{{ static_hidden }}js/hotkey.js"></script>
 <script type="text/javascript" src="{{ static_hidden }}js/notifications.js"></script>
+<script type="text/javascript" src="{{ static_hidden }}js/hashchange.js"></script>
 <script type="text/javascript" src="{{ static_hidden }}js/zephyr.js"></script>
 
 {% if debug %}
diff --git a/tools/jslint/check-all.js b/tools/jslint/check-all.js
index 08ffc36ae3..35972d6d79 100644
--- a/tools/jslint/check-all.js
+++ b/tools/jslint/check-all.js
@@ -45,6 +45,9 @@ var globals =
     // notifications.js
     + ' notifications'
 
+    // hashchange.js
+    + ' hashchange'
+
     // ui.js
     + ' ui'
 
diff --git a/zephyr/static-access-control/4nrjx8cwce2bka8r/js/hashchange.js b/zephyr/static-access-control/4nrjx8cwce2bka8r/js/hashchange.js
new file mode 120000
index 0000000000..1f4df98915
--- /dev/null
+++ b/zephyr/static-access-control/4nrjx8cwce2bka8r/js/hashchange.js
@@ -0,0 +1 @@
+../../../static/js/hashchange.js
\ No newline at end of file
diff --git a/zephyr/static/js/hashchange.js b/zephyr/static/js/hashchange.js
new file mode 100644
index 0000000000..d69f9e9dd1
--- /dev/null
+++ b/zephyr/static/js/hashchange.js
@@ -0,0 +1,38 @@
+var hashchange = (function () {
+
+var exports = {};
+
+var expected_hash = false;
+
+exports.changehash = function (newhash) {
+    expected_hash = newhash;
+    window.location.hash = newhash;
+};
+
+function hashchanged() {
+    // If window.location.hash changed because our app explicitly
+    // changed it, then we don't need to do anything.
+    // (This function only neds to jump into action if it changed
+    // because e.g. the back button was pressed by the user)
+    if (window.location.hash === expected_hash) {
+        return;
+    }
+
+    var hash = window.location.hash.split("/");
+    if (hash[0] === "#narrow") {
+        narrow.hashchanged(hash);
+        ui.update_floating_recipient_bar();
+    }
+    else if (narrow.active()) {
+        narrow.show_all_messages();
+        ui.update_floating_recipient_bar();
+    }
+}
+
+exports.initialize = function () {
+    window.onhashchange = hashchanged;
+};
+
+return exports;
+
+}());
diff --git a/zephyr/static/js/narrow.js b/zephyr/static/js/narrow.js
index eccff6f271..1ec758b8f4 100644
--- a/zephyr/static/js/narrow.js
+++ b/zephyr/static/js/narrow.js
@@ -44,6 +44,40 @@ exports.data = function () {
     return narrowdata;
 };
 
+exports.hashchanged = function (hash) {
+    var full_names, decoded, emails;
+
+    if (hash[1] === "all_private_messages") {
+        exports.all_private_messages();
+    }
+    else if (hash[1] === "stream" && hash[3] === "subject") {
+        exports.by_stream_and_subject_names(decodeURIComponent(hash[2]),
+                                            decodeURIComponent(hash[4]));
+    }
+    else if (hash[1] === "stream") {
+        exports.by_stream_name(decodeURIComponent(hash[2]));
+    }
+    else if (hash[1] === "private_messages") {
+        decoded = decodeURIComponent(hash[2]);
+        emails = decoded.split(", ");
+
+        $.each(emails, function (index, email) {
+            $.each(people_list, function (index, person) {
+                if (person.email === email) {
+                    if (full_names === undefined) {
+                        full_names = person.full_name;
+                    }
+                    else {
+                        full_names += ", " + person.full_name;
+                    }
+                    return false;
+                }
+            });
+        });
+        exports.by_private_message_group(full_names, decoded);
+    }
+};
+
 function do_narrow(new_narrow, bar, time_travel, new_filter) {
     var was_narrowed = exports.active();
 
@@ -120,6 +154,8 @@ exports.target = function (id) {
 };
 
 exports.all_private_messages = function () {
+    hashchange.changehash("#narrow/all_private_messages");
+
     var new_narrow = {type: "all_private_messages"};
     var bar = {icon: 'user', description: 'You and anyone else'};
     do_narrow(new_narrow, bar, false, function (other) {
@@ -135,23 +171,33 @@ exports.by_subject = function () {
         exports.by_recipient();
         return;
     }
+    exports.by_stream_and_subject_names(original.display_recipient,
+                                        original.subject);
+};
 
-    var new_narrow = {type: "subject", recipient_id: original.recipient_id,
-                      subject: original.subject};
+exports.by_stream_and_subject_names = function (stream, subject) {
+    hashchange.changehash("#narrow/stream/" +
+                          encodeURIComponent(stream) +
+                          "/subject/" +
+                          encodeURIComponent(subject));
+
+    var new_narrow = {type: "subject", stream: stream, subject: subject};
     var bar = {
-        icon:        'bullhorn',
-        description: original.display_recipient,
-        subject:     original.subject
+        icon:           'bullhorn',
+        description:    stream,
+        subject:        subject
     };
     do_narrow(new_narrow, bar, false, function (other) {
         return ((other.type === 'stream') &&
-                same_stream_and_subject(original, other));
+                (other.display_recipient === stream &&
+                 other.subject.toLowerCase() === subject.toLowerCase()));
     });
 };
 
-//TODO: There's probably some room to unify this code
-//      with the hotkey-narrowing code below.
 exports.by_stream_name = function (name) {
+    hashchange.changehash("#narrow/stream/" +
+                          encodeURIComponent(name));
+
     var new_narrow = {type: "stream", stream: name};
     var bar = {icon: 'bullhorn', description: name};
     do_narrow(new_narrow, bar, false, function (other) {
@@ -160,43 +206,38 @@ exports.by_stream_name = function (name) {
     });
 };
 
-exports.by_private_message_partner = function (their_name, their_email) {
-    var new_narrow = {type: "private", one_on_one_email: their_email};
-    var bar = {icon: 'user', description: "You and " + their_name};
+exports.by_private_message_group = function (names, emails) {
+    hashchange.changehash("#narrow/private_messages/" +
+                          encodeURIComponent(emails));
+
+    var new_narrow = {type: "private", emails: emails.split(", ")};
+    var bar = {icon: 'user', description: "You and " + names};
     var my_email = email;
     do_narrow(new_narrow, bar, false, function (other) {
         return (other.type === 'private' &&
-                get_private_message_recipient(other, 'email') === their_email);
+                other.reply_to === emails);
     });
 };
 
 // Called for the 'narrow by stream' hotkey.
 exports.by_recipient = function () {
     var message = message_dict[target_id];
-    var bar;
-    var new_narrow;
+    var bar, new_narrow, emails;
     switch (message.type) {
     case 'private':
-        new_narrow = {type: "private", recipient_id: message.recipient_id};
-        bar = {icon: 'user', description: "You and " + message.display_reply_to};
-        do_narrow(new_narrow, bar, false, function (other) {
-            return (other.type === "private" &&
-                    other.reply_to === message.reply_to);
-        });
+        exports.by_private_message_group(message.display_reply_to,
+                                         message.reply_to);
         break;
 
     case 'stream':
-        new_narrow = {type: "stream", recipient_id: message.recipient_id};
-        bar = {icon: 'bullhorn', description: message.display_recipient};
-        do_narrow(new_narrow, bar, false, function (other) {
-            return (other.type === 'stream' &&
-                    message.recipient_id === other.recipient_id);
-        });
+        exports.by_stream_name(message.display_recipient);
         break;
     }
 };
 
 exports.by_search_term = function (term) {
+    hashchange.changehash("#narrow/searchterm/" + encodeURIComponent(term));
+
     var new_narrow = {type: "searchterm", searchterm: term, allow_collapse: false};
     var bar = {icon: 'search', description: 'Messages containing "' + term + '"'};
     var term_lowercase = term.toLowerCase();
@@ -208,6 +249,8 @@ exports.by_search_term = function (term) {
 };
 
 exports.show_all_messages = function () {
+    hashchange.changehash("");
+
     if (!narrowdata) {
         return;
     }
diff --git a/zephyr/static/js/search.js b/zephyr/static/js/search.js
index 16bea5cdd3..8bbdd33785 100644
--- a/zephyr/static/js/search.js
+++ b/zephyr/static/js/search.js
@@ -71,7 +71,7 @@ function narrow_or_search_for_term(item) {
         // unnarrow, it'll leave the searchbox.
         return ""; // Keep the search box empty
     } else if (obj.action === "private_message") {
-        narrow.by_private_message_partner(obj.query.full_name, obj.query.email);
+        narrow.by_private_message_group(obj.query.full_name, obj.query.email);
         return "";
     } else if (obj.action === "search_narrow") {
         narrow.by_search_term(obj.query);
diff --git a/zephyr/static/js/ui.js b/zephyr/static/js/ui.js
index 1e1d0cbcdb..f955aff452 100644
--- a/zephyr/static/js/ui.js
+++ b/zephyr/static/js/ui.js
@@ -176,7 +176,7 @@ function hide_floating_recipient_bar() {
     }
 }
 
-function update_floating_recipient_bar() {
+exports.update_floating_recipient_bar = function () {
     var top_statusbar = $("#top_statusbar");
     var top_statusbar_top = top_statusbar.offset().top;
     var top_statusbar_bottom = top_statusbar_top + top_statusbar.outerHeight();
@@ -239,7 +239,8 @@ function update_floating_recipient_bar() {
     }
 
     replace_floating_recipient_bar(current_label);
-}
+};
+
 function hack_for_floating_recipient_bar() {
     // So, as of this writing, Firefox respects visibility: collapse,
     // but WebKit does not (at least, my Chrome doesn't.)  Instead it
@@ -406,7 +407,7 @@ $(function () {
     $(window).scroll($.throttle(50, function (e) {
         if ($('#home').hasClass('active')) {
             keep_pointer_in_view();
-            update_floating_recipient_bar();
+            exports.update_floating_recipient_bar();
             if (viewport.scrollTop() === 0 &&
                 have_scrolled_away_from_top) {
                 have_scrolled_away_from_top = false;
@@ -590,6 +591,7 @@ $(function () {
     composebox_typeahead.initialize();
     search.initialize();
     notifications.initialize();
+    hashchange.initialize();
 
     $("body").bind('click', function () {
         ui.hide_userinfo_popover();
diff --git a/zephyr/tests.py b/zephyr/tests.py
index 298e4eda66..8b5cb34d03 100644
--- a/zephyr/tests.py
+++ b/zephyr/tests.py
@@ -643,12 +643,12 @@ class GetOldMessagesTest(AuthedTestCase):
 
     def test_bad_narrow_one_on_one_email_content(self):
         """
-        If an invalid one_on_one_email is requested in get_old_messages, an
+        If an invalid 'emails' is requested in get_old_messages, an
         error is returned.
         """
         self.login("hamlet@humbughq.com")
-        bad_stream_content = ("non-existent email", 0, [])
-        self.exercise_bad_narrow_content("one_on_one_email", bad_stream_content)
+        bad_stream_content = (["non-existent email"], "non-existent email", 0, [])
+        self.exercise_bad_narrow_content("emails", bad_stream_content)
 
 class DummyHandler(object):
     def __init__(self, assert_callback):
diff --git a/zephyr/views.py b/zephyr/views.py
index 3d1d5b81b4..85b9e3e0f4 100644
--- a/zephyr/views.py
+++ b/zephyr/views.py
@@ -283,20 +283,28 @@ def get_old_messages_backend(request, anchor = POST(converter=to_non_negative_in
         recipient = Recipient.objects.get(type=Recipient.STREAM, type_id=stream.id)
         query = query.filter(recipient_id = recipient.id)
 
-    if 'one_on_one_email' in narrow:
+    if 'emails' in narrow and (type(narrow['emails']) != type([]) or len(narrow['emails']) == 0):
+        return json_error("Invalid emails %s" % (narrow['emails'],))
+    elif 'emails' in narrow and len(narrow['emails']) == 1:
         query = query.filter(recipient__type=Recipient.PERSONAL)
         try:
-            recipient_user = UserProfile.objects.get(user__email = narrow['one_on_one_email'])
+            recipient_user = UserProfile.objects.get(user__email = narrow['emails'][0])
         except UserProfile.DoesNotExist:
-            return json_error("Invalid one_on_one_email %s" % (narrow['one_on_one_email'],))
+            return json_error("Invalid emails ['" + narrow['emails'][0] + "']")
         recipient = Recipient.objects.get(type=Recipient.PERSONAL, type_id=recipient_user.id)
         # If we are narrowed to personals with ourself, we want to search for personals where the user
-        # with address "one_on_one_email" is the sender *and* the recipient, not personals where the user
-        # with address "one_on_one_email is the sender *or* the recipient.
-        if narrow['one_on_one_email'] == user_profile.user.email:
-            query = query.filter(Q(sender__user__email=narrow['one_on_one_email']) & Q(recipient=recipient))
+        # with the desired e-mail address is the sender *and* the recipient, not personals where the
+        # user with the desired e-mail address is the sender *or* the recipient.
+        if narrow['emails'][0] == user_profile.user.email:
+            query = query.filter(Q(sender__user__email=narrow['emails'][0]) & Q(recipient=recipient))
         else:
-            query = query.filter(Q(sender__user__email=narrow['one_on_one_email']) | Q(recipient=recipient))
+            query = query.filter(Q(sender__user__email=narrow['emails'][0]) | Q(recipient=recipient))
+    elif 'emails' in narrow:
+        try:
+            recipient = recipient_for_emails(narrow['emails'], False, user_profile, user_profile)
+        except ValidationError, e:
+            return json_error(e.messages[0])
+        query = query.filter(recipient=recipient)
     elif 'type' in narrow and (narrow['type'] == "private" or narrow['type'] == "all_private_messages"):
         query = query.filter(Q(recipient__type=Recipient.PERSONAL) | Q(recipient__type=Recipient.HUDDLE))
 
@@ -611,6 +619,32 @@ def create_mirrored_message_users(request, user_profile, recipients):
     sender = UserProfile.objects.get(user__email=sender_email)
     return (True, sender)
 
+def recipient_for_emails(emails, not_forged_zephyr_mirror, user_profile, sender):
+    recipient_profile_ids = set()
+    for email in emails:
+        try:
+            recipient_profile_ids.add(UserProfile.objects.get(user__email__iexact=email).id)
+        except UserProfile.DoesNotExist:
+            raise ValidationError("Invalid email '%s'" % (email,))
+
+        if not_forged_zephyr_mirror and user_profile.id not in recipient_profile_ids:
+            raise ValidationError("User not authorized for this query")
+
+    # If the private message is just between the sender and
+    # another person, force it to be a personal internally
+    if (len(recipient_profile_ids) == 2
+        and sender.id in recipient_profile_ids):
+        recipient_profile_ids.remove(sender.id)
+
+    if len(recipient_profile_ids) > 1:
+        # Make sure the sender is included in huddle messages
+        recipient_profile_ids.add(sender.id)
+        huddle = get_huddle(list(recipient_profile_ids))
+        return Recipient.objects.get(type_id=huddle.id, type=Recipient.HUDDLE)
+    else:
+        return Recipient.objects.get(type_id=list(recipient_profile_ids)[0],
+                                     type=Recipient.PERSONAL)
+
 # We do not @require_login for send_message_backend, since it is used
 # both from the API and the web service.  Code calling
 # send_message_backend should either check the API key or check that
@@ -683,31 +717,11 @@ def send_message_backend(request, user_profile, client,
             return json_error("Stream does not exist")
         recipient = Recipient.objects.get(type_id=stream.id, type=Recipient.STREAM)
     elif message_type_name == 'private':
-        recipient_profile_ids = set()
-        for email in message_to:
-            try:
-                recipient_profile_ids.add(UserProfile.objects.get(user__email__iexact=email).id)
-            except UserProfile.DoesNotExist:
-                return json_error("Invalid email '%s'" % (email,))
-
-        if client.name == "zephyr_mirror":
-            if user_profile.id not in recipient_profile_ids and not forged:
-                return json_error("User not authorized for this query")
-
-        # If the private message is just between the sender and
-        # another person, force it to be a personal internally
-        if (len(recipient_profile_ids) == 2
-            and sender.id in recipient_profile_ids):
-            recipient_profile_ids.remove(sender.id)
-
-        if len(recipient_profile_ids) > 1:
-            # Make sure the sender is included in huddle messages
-            recipient_profile_ids.add(sender.id)
-            huddle = get_huddle(list(recipient_profile_ids))
-            recipient = Recipient.objects.get(type_id=huddle.id, type=Recipient.HUDDLE)
-        else:
-            recipient = Recipient.objects.get(type_id=list(recipient_profile_ids)[0],
-                                              type=Recipient.PERSONAL)
+        not_forged_zephyr_mirror = client and client.name == "zephyr_mirror" and not forged
+        try:
+            recipient = recipient_for_emails(message_to, not_forged_zephyr_mirror, user_profile, sender)
+        except ValidationError, e:
+            return json_error(e.messages[0])
     else:
         return json_error("Invalid message type")