diff --git a/securedrop/create-dev-data.py b/securedrop/create-dev-data.py
index d082c9bf176..6100b7a9de8 100755
--- a/securedrop/create-dev-data.py
+++ b/securedrop/create-dev-data.py
@@ -16,7 +16,7 @@
 
 from sdconfig import config
 from db import db
-from models import Journalist, Reply, SeenReply, Source, Submission
+from models import Journalist, Reply, SeenFile, SeenMessage, SeenReply, Source, Submission
 from specialstrings import strings
 
 
@@ -65,7 +65,14 @@ def main(staging=False):
                     i, num_sources, journalist_who_replied=journalist_tobe_deleted
                 )
                 continue
-            create_dev_data(i, num_sources)
+
+            # Mark a third of sources as "seen", a third as "semi-seen", and a third as "unseen"
+            if i % 3 == 0:
+                create_dev_data(i, num_sources, seen_files=2, seen_messages=2)
+            elif i % 3 == 1:
+                create_dev_data(i, num_sources, seen_files=1, seen_messages=1)
+            else:
+                create_dev_data(i, num_sources)
 
         # Now let us delete one journalist
         db.session.delete(journalist_tobe_deleted)
@@ -98,6 +105,8 @@ def create_dev_data(
     num_files=2,
     num_messages=2,
     num_replies=2,
+    seen_files=0,
+    seen_messages=0,
     journalist_who_replied=None  # noqa: W605, E501
 ):
     # Store source in database
@@ -113,7 +122,14 @@ def create_dev_data(
     os.mkdir(current_app.storage.path(source.filesystem_id))
     current_app.crypto_util.genkeypair(source.filesystem_id, codename)
 
+    # TODO: Add variety for journalists who make replies and journalists who "see" submissions
+    if not journalist_who_replied:
+        journalist = Journalist.query.first()
+    else:
+        journalist = journalist_who_replied
+
     # Generate some test messages
+    seen_messages_count = 0
     for _ in range(num_messages):
         source.interaction_count += 1
         submission_text = next(messages)
@@ -126,8 +142,13 @@ def create_dev_data(
         source.last_updated = datetime.datetime.utcnow()
         submission = Submission(source, fpath)
         db.session.add(submission)
+        if seen_messages_count < seen_messages:
+            seen_messages_count = seen_messages_count + 1
+            seen_message = SeenMessage(message_id=submission.id, journalist_id=journalist.id)
+            db.session.add(seen_message)
 
     # Generate some test files
+    seen_files_count = 0
     for _ in range(num_files):
         source.interaction_count += 1
         fpath = current_app.storage.save_file_submission(
@@ -140,6 +161,10 @@ def create_dev_data(
         source.last_updated = datetime.datetime.utcnow()
         submission = Submission(source, fpath)
         db.session.add(submission)
+        if seen_files_count < seen_files:
+            seen_files_count = seen_files_count + 1
+            seen_file = SeenFile(file_id=submission.id, journalist_id=journalist.id)
+            db.session.add(seen_file)
 
     # Generate some test replies
     for _ in range(num_replies):
@@ -152,10 +177,6 @@ def create_dev_data(
              config.JOURNALIST_KEY],
             current_app.storage.path(source.filesystem_id, fname))
 
-        if not journalist_who_replied:
-            journalist = Journalist.query.first()
-        else:
-            journalist = journalist_who_replied
         reply = Reply(journalist, source, fname)
         db.session.add(reply)
         db.session.flush()