Horses pull a grain reaper at Hilltop Farm, Deerfield, Massachusetts, in the 1920s. Although gas-powered tractors were widely available by then, many farmers continued to use their horses. The reaper pictured here follows a design from the 1880s, based on ideas first pioneered by Cyrus McCormick. It cuts grains, bundles using twine, and then the bundles are allowed to dry for a few days. Later, they will be threshed (a process that separates the seeds from the stalks).