SD 204 begins in
Stanley County at an intersection between
SD 1806 and an access road, which leads to some of the dam's facilities as well as the
Oahe Downstream Recreation Area, located at the base of the dam near one of the spillways. The highway climbs up a gradual grade as it curves northeastward, climbing up to the very top of the dam, where it has a y-intersection with a service road. SD 204 run due northeast directly across the dam for nearly 1.5 miles, offering views of the lake and the valley below as it crosses into
Hughes County at the site of the original
Missouri River basin, before having an intersection with an access road to the power house and pulling away from the dam. The highway passes by the historic Oahe Chapel before coming to an end at an intersection with
SD 1804 several miles north of
Pierre. The entire length of South Dakota Highway 204 is a rural, two-lane, state highway. ==History==