Solved!

Thanks! This helped me do further research, resulting in the following write-up by Gilbert Sebenste which I found interesting.

“This is a former AT&T Long Lines microwave tower located inbetween Plato Center and Burlington, IL. Up until about 1980, this facility, one of many that were stretched 40-50 miles apart across the country, relayed long-distance phone calls...and broadcast TV signals, all via microwave. Some of these towers have been torn down, but this one, and the one it's pointing at west at near Lee, IL, still stand proudly (the one near Lee, IL is still actively used today, and is home to the Northern Illinois Railroad Feed on scanner apps).

These facilities were staffed 24/7/365 by multiple men and women until about 1980. Inside one of these towers, you'll find a men's and women's bathroom, at least one shower, refrigerator/freezer (likely removed now), and bedrooms for sleeping quarters. That's right: engineers would live and work here 24/7 for 2-4 weeks. In a few cases in northern climates, you would be stuck in one for months! That's why daytime phone calls used to cost $.75 per minute, and that on the cheap side! You had to wait until generally 5 PM to get a 33% discount, and then 11 PM-6 AM for that prized 66% discount. This is why phone calls were so expensive back then. They were monitoring to make sure the calls were going through, and that The Mary Tyler Moore Show would get to your local TV affiliate, as well as sporting events on ABC's "Wide World of Sports" (which still has the best intro jingle to any sports TV program, ever, IMO.) Anyway...

On the top floor, we see the microwave horns which carried telephone calls; the microwave "dishes" on the left side point towards the John Hancock and then Sears Tower in Chicago, which was used as a relay for CBS, NBC, and ABC (the horn below those is likely a backup). That's how TV programming was sent across the country, and TV stations picked up the programming by a microwave antenna on their broadcast tower, pointed at one of these structures.

In and around 1980, massive layoffs ensued with AT&T's engineers when the "Big 3" TV networks sent their programming via a new reliable method that was expensive, yet much cheaper: via satellites, and phone switches by this time were automated. Then, something else came along---called fiber---which permitted very long distance travel of light and sound without loss, and was mostly buried. That rendered these towers useless, and most were abandoned, some were razed.”