High Quality Content by WIKIPEDIA articles! Oacoma is a town in Lyman County, South Dakota, United States. The population was 390 at the 2000 census. Oacoma is located on the west bank of the Missouri River, across from Chamberlain. As of the census of 2000, there were 390 people, 169 households, and 111 families residing in the town. The population density was 192.8 people per square mile (74.5/km2). There were 188 housing units at an average density of 92.9/sq mi (35.9/km2). The racial makeup of the town was 94.36% White, 3.33% Native American, and 2.31% from two or more races. Hispanic or Latino of any race were 0.26% of the population.