No. 21

The story

Massey-Harris built its first self-propelled combine, the No. 20, in 1938, but it was too heavy and costly to mass produce. Australian engineer Tom Carroll designed the lighter No. 21, tested in 1940 and on sale from 1941, often described as the first rubber-tyred self-propelled combine.

Wartime steel rationing held output back until 1944, when US vice president Joe Tucker won approval for 500 extra machines in the Harvest Brigade. Sold only to custom operators who pledged to cut at least 2,000 acres, the fleet worked north from Texas into Canada and harvested more than a million acres.

By 1947 Massey-Harris held over half the American combine market, and about 10,000 were built in 1949 alone.