Well, it's only part of the antenna, and it has been out of service since 2013. It's the main component of an abandoned Air Force facility just north of Maricopa, Arizona. The facility was part of the Air Force's "space fence" system, a set of transmitters and receivers that detects objects orbiting the earth, including space debris.

Its modest buildings are clearly visible from the nearby highway (SR 347). Every time I drive between Maricopa and Phoenix I see it and for a while I wondered what the place was. That led to examination in Wikimapia, which shed light on the facility and the system of which it was a part. The facility was vacated in October 2013.

A chain-link fence, topped with barbed wire, still surrounds the facility. A few buildings still stand, boarded up, but some doors stand open, as if the buildings are being aired out. This is the northern end of the antenna; the southern portion of the antenna is missing. This view is eastward.

More information is in this Wikipedia article.