The Farmer’s Locomotive These enormous steam-powered machines are the ancestors of the modern tractor. Sometimes called road locomotives, these smoke-belching monsters were first produced in quantity in the 1870s. By 1900, some thirty firms were producing 5,000 traction engines a year, and they continued to be manufactured until the late 1930s. Though they were used for many tasks, such as powering portable sawmills and rock crushers, their primary use was to drive threshing machines during grain harvests. Their close cousins, the steam shovel and the steam roller, helped build endless miles of roads. These machines were simple, powerful, and durable -- some were still in use for threshing as recently as the late 1950s, when they were finally completely replaced by the modern combine. The example in the Smithsonian’s collection was in continuous use for harvesting grain from 1877 until 1950.