Thousands and thousands of 5 and 6 foot pull type combines were used up until into 1950's which were a big improvement over binders and threshing machines use previously.  Ear corn was harvested with a one or two row picker.  A big tractor was a Farmall M or a John Deere A, and farms were much smaller.  A BTO might farm a whole section.  And there were a lot more farmers.  Times change. 

BTW, Massey Harris had a 7 foot self-propelled Clipper combine too which was a sp version of the pull type Clipper which was a straight through machine with about a 5 foot wide cylinder.