Two revolutions in American agriculture reflect the impact of technological change on farming during the past century. The first revolution saw the change from manpower to animal power, and centered about the Civil War. The second revolution saw the change from animal power to mechanical power and the adaptation of chemistry to agricultural production. It centered around the post-World War II period. The transition from animal power to mechanical power is virtually complete. In 1962, the Statistical Reporting Service of the United States Department of Agriculture discontinued reporting the number of horses and mules on farms. They were no longer of significance to farm production.