Nixon spent a lot of time in the winter in Florida, and there was sort of a tradition of nicknaming presidents’ alternate sites, so Post donated this place to be the Winter White House, but Nixon preferred to stay on at the mansion of his pal Bebe Rebozo and apparently didn’t use it much. Then later presidents had their own places to go they didn’t all want to spend time in Florida so it went idle.
The Bebe Rebozo place was in San Clemente, CA, and was designated “The Western White House”.