Cell Towers displays cell tower locations within the United States based on data from the Federal Communications website in 2017.
Once the data is loaded and the map position moves to the United States, zoom in a good amount to the location of interest, then do a long-tap (3 seconds) on the map to display the tower locations within the chosen radius (5 km is the default). Tap a marker to see the licensees at that location.
The data is not 100% accurate since you will find locations in the middle of nowhere with no tower visible in the aerial view, and I know of towers not listed. This is most likely due to errors in the latitude and longitude given for an item. Use the app for entertainment and not for any crucial work.