I had never heard of Bush Hog tractors until I saw this post. Looks like a well built machine. They must have been regional and not popular in the midwest. Wheel Horse is somewhat like that as well, not many around this area.
They were built in Galesburg, Kansas. I found this one in the upper left corner of Ohio. I have 3 other Bush Hog tractors...all 3 are D4-10 models. Most I see for sale are from east of the Mississippi and many in the New England area.