Extinct animals, discontinued cars and disarmed rockets meet their end at the Great Plains. Grass covers many a secret and is a great backdrop for modern art installations. You get extra points for confounding future archeologist: just to think that we may know as little about Stonehenge as they will deduce about Carhenge.
In the 19th century prairie provided in abundance: land was parceled out to whoever would claim it, bones were dug up and carted off to whichever museum sponsored the dig. Military installations served the immediate purpose of suppressing native population.
The 20th century shrunk the plains. It's all about conservation, preservation and recycling now. Finally somebody figured out that it is cheaper to send paleontologists to the bones, not the other way around. With tribes persuaded to stay on reservations the military is free to engage in world wide conflicts. And perfect location for retaliatory missiles aimed at targets in the Soviet Union is now a good location for a cold war era museum. Cars are still everywhere, but once they reach certain age, they are shredded and sent overseas instead of providing material for artwork.
Diversions that we find amid the grass detract from the sad truth: the prairie as the first Europeans knew it is gone. And digging bones, installing defense system or bringing in cars contributed but a little to its destruction. When we cracked the agriculture thing - it's water, stupid - and the plains became the America's bread basket, we signed their death warrant. So former bone beds digs, cars as art and decommissioned missile silos are the apt memento.