Okay, somebody please explain “grain elevator”. Does it have some sort of “first in-first out” function built into its design, or is it merely intended to keep the grain “elevated” off the ground?
(At last, I get to use my Illinois farm roots in GQ. 
) Later ones were made with wire. The earlier ones are as you describe - wooden and rectangular.
Those not interested in nostalgia should skip the rest of this.
When I was a wee lad, we were in the last days of crib usage (at least on our farm). We had a two-row corn picker, mounted on a tractor, that would strip the ears off the stalks and propel them into a wagon pulled behind the tractor. It was a nasty job: sitting on an open-platform tractor (no cab to keep the operator warm in cold weather) with very loud mechanical noise being fed into both ears from close proximity. The second man (my uncle) would come out to the field on another tractor, grab the filled wagons, and haul them back to the crib. An electrically-powered machine (a long incline with moving chains and paddles) would send the corn up to the top of the crib to be distributed around the crib by a series of movable chutes. Come spring, when the corn was dry, a specialist corn sheller would come by and use his (usually truck-mounted) machinery to remove the kernels from the cob and deposit them in trucks for transport to the local grain elevator.
I was probably age 13 or so the last time we did this. The thing I remember most about that involves our farm animals. We had a female collie and a big, yellow-orange, mean tomcat. (This was Harfy. I have told one of his stories on another thread.) As the shelling proceded, rats were running from the crib. Dog and Kat killed dozens of them. Not to eat - just to kill them. :eek:
Even more nostalgically, that particular corn crib had a bit of history. Sometime back in the early 20th century, my great uncle Pete* bought some land from a distressed neighbor. A crib sat on the property, which otherwise had no buildings. He hired a steam tractor to come out and drag the crib over to the home place, and it was subsequently rebuilt to increase its volume by a factor of 8 or so.
Fast-forward to the 21st century. It is fated to be razed, so I went in to salvage as many of the original boards as possible. Doper woodworkers who use quarter-sawn white oak for their projects may wonder where the flat-sawn boards go. At one time, they went into corn cribs. I have a couple hundred board-feet of them. 
An interesting grain when stained.
*Pete was a real character. In his day, he was bigger than most and strong as an ox. Great-grandad would assign his boys so much corn to pick each day (by hand, of course). Pete would get up before dawn, and pick starting off with lanterns, so he could be done by noon. Then he would go to town to play football with the other stout young men.
I must protest! You can not write about my childhood as if it were you’re own! 
You’re on the right track. The cylindrical bins are open at the top (they’re protected from the weather by the “house” on top of the elevator) and filled from the top. Incoming grain is conveyed up to the top (the “elevator” part of the grain elevator) and dumped on a conveyor belt that moves the grain to whichever bin is being filled. The bins are emptied from the bottom, an underground conveyor system taking the grain to the point where the stuff is dumped into trucks or railroad hopper cars or whatever. I think the whole system is designed so they can move grain from one bin to another. (I’m vague on this, but internal heat build-up seems to be a problem and they have to move the grain around occasionaly; at any rate, I can say for certain that the bins have temperature sensors in them.)
(It’s a messy system, and grain dust in the air is a problem. In the right concentration the stuff is explosive.)
While this design does keep grain off the ground, I think that’s just a side benefit. (Full elevators during harvest time have been know to temporarily keep piles of grain on the ground.) I know from personal observation that a leaky roof can be a problem - the grain at the top of the bin will sprout and grow.
Despite any irritations associated with my current office job, I can always reflect that I no longer have to climb up into a silo on a cold winter’s day, chip off frozen silage with a fork that has at least one broken tine, and throw it down to ravenous cattle, with a large percentage of said silage blowing back in the cold wind into my clothes.
One thing I learned when I was young – good, hard, honest work is for suckers.