While roaming around, I have happen to come across a number of iron doors. Its wild how they tend to outlive the entire building to which they were connected.
Here are a few examples.
Ruins in the near ghost town of Hornitos, CA.
Ruins in the ghost town of Bodie, CA (Bodie State Park)
Ruins in the near-ghost town of Bear Valley, CA
Maybe I will spot more as I travel... Feel free to send any photos of cast iron remains to us and we will post!