The SAGE (Semi Automatic Ground Environment) continental air defense system was developed by the Massachusetts Institute of Technology's (MIT) Digital Computer Lab, the Air Force Cambridge Research Lab and MIT's Lincoln Lab between 1950 and 1957. In 1958, one month after the first SAGE center was built at McGuire AFB, MITRE was incorporated as a private, non-profit corporation to provide engineering and technical services to the federal government.
One of the test sites for the SAGE system was constructed in Bath, ME in 1955. This site was used to test FPS-31 frequency diverse search radar and FPS-6 search and height-finder radar.
The site is still largely intact today and can easily be found along Route 24 between Bath and Brunswick. Tower Lane is located at 238 State Rd (aka Route 24) in West Bath. You can see the tower from a long way off, so it's not too difficult to find.
The site is now home to a metal recycler of sorts. The day I visited there were people on site and working, so I didn't climb the tower. The tower appears to be in very good condition and the original support buildings are still intact, though they have been added on to.
These pictures were taken on about the hottest day of the year (summer 2009). I was in the Brunswick area, picking up some 062 casting Vortec heads and decided to swing in and check out the site.
I hope to be returning soon to actually climb the tower and gather some more pictures.