We first visited Pigeon Key in 1969 when our car (a 1932 Plymouth) broke down on 7 mile bridge. My husband pushed, I steered and we drifted down onto Pigeon Key where he fixed the fault. All that was there when we were there were old boarded up wooden buildings.
Now Pigeon Key (like the old 7 Mile Bridge) is on the National Register of Historic Places. It was the home base for Flagler's Key West Extension of the Florida East Coast (FEC) Railway workers.
Flagler's Seven-Mile Bridge was considered an engineering feat. The modern Seven-Mile Bridge no longer goes to Pigeon Key (picture from the car on the new bridge) so the old bridge is a fitness path and fishing pier. From Marathon, the old bridge does not go much past Pigeon Key. The middle section is still there, but abandoned. there's no access to it from land from either side.
Some of Pigeon Key's wood frame structures are colored in Flagler's trademark yellow but many of them are still painted white.
The Pigeon Key Foundation manages the island. Among the foundation's completed projects: "Transforming one Pigeon Key structure into a railroad museum. Here, on view to the public, are historic artifacts from the FEC Railway, including concrete "bones" that served to test the strength of mixtures used in erecting the Old Seven-Mile Bridge. Photographs feature the trains of the railway, the making of the original bridge, the buildings of Pigeon Key, and the island's former inhabitants."
Pigeon Key is reached either by foot or bike on the old bridge (over 2 miles) (except during the art show in February when no walkers or bikers are admitted to the old bridge) or by shuttle service from the Pigeon Key Visitor Center and Gift Shop on Knight's Key, mile marker 47 oceanside. Picture shows the little shuttle. Regardless of the way you get there, admission to the island costs $7 per adult and $4 per student (children are admitted free). Proceeds benefit the Pigeon Key Foundation.