The main road through Green River was added to the state highway system in 1912 and numbered as part of US-50 in the 1920s. The state legislature defined the portion through Green River as State Route 19 in 1969, although the bypass on I-70 had not yet been built. Construction had begun in the mid-1980s, and when finished, the old route, along with a new connection to exit 164, became SR-19.