More and more kerosene or gasoline tractors power threshers, which are becoming smaller. At first, the tractors are large, but successful manufacturers soon recognize the need to build small tractors. Collaboration among neighbors during the threshing season gradually diminishes. On the Great Plains, combines enjoy increasing favor. Throughout the grain farming regions of the United States, small combines pulled by tractors become more and more popular.
Farmers combine their grain independently of one another.
During World War II, many steam engines are scrapped. Others become derelict.