John Deere tried to develop their own tractor in the late teens and early twenties. They had a pretty good one in the Dain AWD, but before 100 were finished, Joe Dain unexpectedly died. After that, Deere did what they've done many times since, they found the best company making the product they wanted to sell, and bought them. This time, it was the Waterloo Boy tractor company of Waterloo, IA in about 1923. Waterloo Boy tractors used the same engine configuration that Deere would use until 1959, the two cylinder horizontal engine. Deere developed a new tractor at that factory, the John Deere Model D, which stayed in the line until 1952.
Meanwhile, at McCormick-Deering, the Farmall was introduced, which was the first tractor that could plow, cultivate, mow, and whatever else separate machines had always done. Farmall remained in the number one sales position until 1960. Deere answered with the Models A and B in 1932, both of which had a good following, but could never quite match the sales of Farmall. Deere continued with the two cylinder engine because it was everything Mike said above, plus rugged. It was easy to work on, and cheap to run. Deere tested their tractors on their own test farms, mainly the rice and cane farms down south, and if anything failed, it was back to the drawing board. It's been said that a few weeks at a rice or cane farm would reduce a Farmall to scrap metal, but the Deeres would keep going. Unfortunately for Deere, most farmers didn't raise rice or cane, so the Farmalls stayed ahead in sales, mainly because they offered about five more horsepower for the same money.
In 1949, Deere made their last power improvements on the two cylinder, and the writing was on the wall. They started a multi-cylinder project in 1953 that was one of the best kept secrets of all time. By making small improvements to the existing two cylinder tractors, they were able to keep loyalty to the brand. Deere introduced the Next Generation of 4 and 6 cylinder tractors at the "Deere Day in Dallas" event in 1960. Deere immediately took over the number one spot in sales from Farmall (by then International) and has remained there since.
This has been a very brief history of Deere and Company, totally from memory, so I'm sure I made some mistakes.
Anyway, my now 70 year old John Deere AR is still popping along, doing way more work than its 37 HP would indicate. That's drawbar HP, not engine HP as they are now measured.
