In 1930 and 1931, State Highway 204 extended south future Route 20 in Hartland, along the east bank of the east branch of the Farmington River, to future US 44 in New Hartford. Its northern terminus was near the western end of Walnut Hill Road in Hartland.

On Jan. 1, 1932, SH 204 was renumbered to Route 179 – an older alignment of today's Route 179.

Most of SH 204 is no longer open to traffic, and part of it is even underwater, because the area was flooded to create the Barkhamsted Reservoir. See more information at the Route 179 page.