In addition to the links above, also use this:
This will let you search for antenna structures (towers) in the area. I've found that ASR info and ULS info can be significantly different, and the two systems are NOT cross referenced, so this could open up some new information for you. Also don't forget the link on RR licence info pages for other nearby licences. You'll just need to convert the coordinates between decimal form and degrees/minutes/seconds. (RRdatabase displays coordinates in decimal form, but queries to FCC database are in degrees/minutes form, no seconds)
Any tower taller than 60 feet (21 meters) must be registered and assessed by FAA. Shorter towers may or may not appear in the ASR system and should be found in the ULS, as well as any antenna mounted on a building, pole, water tower, bridge, etc.
Also, keep in mind that errors exist. Down the street from me is a short tower with a three-element array for the City of Lakeland (FL) trunking system. I doesn't show up on the ASR system, and the ULS location coordinates have 00 for the seconds in both latitude and longitude, placing it several hundred feet from where it actuall is!
Here in Florida, Rand McNally has some nice street map books. The grid system they use is based on GPS coordinates, on half-minute intervals. Makes it real easy to locate/plot out license and ASR sites. I also have a hand-held Garmin I take on the road, mark a waypoint when I pass an interesting site and lookup the coords later to see what's there (think they call that geocartography). Since I'm new to the area (less than a year) it's been great for learning my way around and finding whats out there.