Looking it up on the Henderson Beach State Park website says this is a Clausen Tracking Site that was established in 1951 for national security and rocketry testing.
Forgive me for intruding a photo into your excellent trip report, however, if you visit the Canaveral National Seashore (Cape Canaveral, Indian River region), these old tracking sites (built way back in the '50s) were for down-range test observations. This is me (a few weeks ago: end of February) at the National Seashore:
I was watching the Falcon 9 (DSCOVR-USAF) deep space weather rocket launch; the spent rocket of which was not retrieved by SpaceX retrieval ocean-going landing platform drone ship
here--> (I won't clutter up your trip report with any other photos)...
Cheers; and again, an excellent trip report!
Silver-
