Florida

https://www.cnn.com/travel/article/everglades-jetport-florida-cmd/index.html

It was supposed to be the world’s largest airport, a glamorous intercontinental hub for supersonic airliners with six runways and high-speed rail links to surrounding cities. But today, it’s little more than an airstrip in the middle of nowhere.

The Everglades Jetport, as it was called when the project launched in 1968, started its life right at the end of the Golden Age of air travel, when plane cabins were filled with the smoke of cigars and the clinking of silverware.
...
Now, that lone runway functions both as a training ground and a nostalgic reminder of a dream that never materialized.