Junk yards usually scrapped cars after the good stuff had been stripped. I wonder how many frames and (savable today) bodies went to the crusher as they made room for newer cars?
In the 70s the "Pick-A-Part" business model came into vogue. They'd haul the cars in and neatly put them in rows on jack stands. After they were there for about a month what was left was pulled out and crushed on the spot. The car pancakes were stacked on a semi and taken to LA Harbor. There they had a large chipper they fed the cars into and it spit little chunks into a ships hold to be recycled in Japan into new Toyotas, Hondas, etc.
We used to watch them prep the cars to be crushed. They had a giant forklift. The forks were about 10' long. It also had a claw. They would lay the forks on the front fenders and the claw would reach in and yank the engine/trans out - nothing was unbolted it was brute strength. Then they would flip the car over and spear the gas tank out. Those and the engine went into piles the rest went on the crusher.
I looked for a video on the process. Today they have gotten more sophisticated. They target specific materials - aluminum, copper wiring, cast iron rotors, etc. It still takes less than 10 minutes.
https://www.youtube.com/watch?v=y3__cghqyOU
The LA Harbor shredder - About every six months they pay to clean all the rust spots from the boats in the adjacent marina.
https://www.youtube.com/watch?v=Ix7eEk0G1B0