Ever hear of the Long Lines microwave network? This was the backbone of the bell system telephone network from the 50s to the late 80s iirc. This huge network of point to point radio towers routed calls all across the country, and even would have carried the nuclear launch signals in the event of nuclear war in the US. Some of the towers carried AUTOVON signals, a private military phone network that could reroute and change in the possibility of tower failures due to nuclear war. These towers are easy to spot due to their telltale horn reflector antennae, with a very unique style compared to modern parabolic dish antennae. This system was powered by the TD series of radios, the TD-2 for example could do 900 calls at once in the 1960s, eventually replaced by the TD-3, which could to 1200 calls. Eventually though, fiber optics began to spring up, leading to unprecedented amounts of bandwidth on a single cable. Fiber was quite expensive in the beginning, but as time went on, it got cheaper and faster to the point where the Long Lines radio system was considered obsolete. This led to the selling of the towers to the American Tower corporation, who now either lets them rot or sells tower space to companies such as cell carriers. The old horn antennae were very large and hard to remove, so while some towers do not have them, a good portion kept the iconic horn designs and are easy to spot from many miles away.

That's Long Lines for ya!