For much of the 20th century, the backbone of the AT&T "Long Lines" long distance telephone network consisted primarily of terrestrial microwave links (rather than copper or fiber cables). Towers with distinctive KS-15676 "horn" antennas could be seen on hilltops and atop switching center buildings across the US; they were simply part of the American landscape.
Most of the relay towers were simple steel structures. This brutalist concrete platform in San Jose was, I believe, of a unique design.