descol
Washington-Hoover was closed immediately after Washington National KDCA opened less than one mile south of it in June 1941. The Pentagon was built in 21 months where Washington Hoover had been located. Construction of the Pentagon started in September 1941.
I think you will find that the swimming pool was a completely separate operation.
In my early youth, I'd get my parents to park on a little hill south/SE of Hoover Field so I could watch the planes. The only type I can remember is the Pennsylvania Central Airlines DC-2. Too bad I can't remember the older types. Oops, I just admitted how old I am.