A friend is a train buff, subscribes to train magazines, etc. He once sent me an article on one of the largest peacetime train transports of all time. I was a participant. 1957 BSA national Jamboree, Valley Forge, PA. All the scouts arrived by train.
Funniest aside was when there was a problem with the track ahead of us, so our train was placed on a siding near a tiny town (maybe population 200) in North Dakota. We were turned loose. 800 scouts invading the poor town. Had to be the greatest biz day ever seen by this town. When we pulled out, there wasn't a can of pop or a candy bar to be had.