In the early years, the famous marquee was switched during football season.
When the bleachers were added in the late '30s, the football layout was very tight.
The field ran along the third base line. A temporary stand was built in right field.
The endzone in left field ran right up to the brick wall. There was very little room beyond the back of the endzone.
Things were even worse in the other endzone. It ran right up to the first base dugout. There were plywood sheets put up to cover the dugout. But the corner of the endzone was not a full ten yards. That tells you how much influence George Halas had in the NFL. His field didn't have to be regulation size.