Probably depends "where". I realize we're not the center of the universe, but I never saw one farming in our area. Tractor pulls, yes. I realize AC called it a row crop tractor, but I'm not sure 18.4 tires were available for the D21, were they? If no 18.4 tires, then row cropping was impossible. There were almost no standard tread tractors in our area (NE IL) in those days.

AC built them for 6 years. They built fewer D21s in those 6 years than IH built 1206s in 2 years. D21 came out in '63, 1206 came out in '65. D21 started out as a no-blower tractor, then added the blower after IH intro'd the 1206. D21 had more hp than the 1206, but also 60 cubes bigger (that would be like .9999L for Candians & Europeans).

Personally, I think tractor pulling is what made D21s admired. They are brutish looking, no doubt.