Massey-Harris Model 20 Self-Propelled Combine in Use, Eastern Washington, circa 1940

"Combines" combine the major tasks of grain harvest: cutting and gathering the crop, threshing and separating the kernels from the chaff, and disposing of the straw. The Massey-Harris Model 20, introduced in 1938, culminated over 100 years of mechanical improvements. One driver operated the self-propelled machine, which reduced the need for hired help during the labor shortages of World War II.