The Bears played at Wrigley Field before moving to Soldiers Field. The left field wall was the back line of the northern end of the field. There was not enough room at the southern end for a full end zone as one end of it was cut so the end zone was not a rectangle. The field is no bigger now so I don't see how they can play there.
I just found a picture from 1963 - maybe it is just barely big enough.