County Seat: De Smet
Square Miles: 838
The county seat was created in 1880 and named for two brothers prominent in territorial affairs. De Smet was the home of Laura Ingalls Wilder and a nearby Manchester farm ws the home of famed artist Harvey Dunn. The first post office was located at Arlington in 1880, at one time named Nordland, then Denver, before finally becoming Arlington. Spirit Mound, Spirit Lake and Spirit Lake Mounds are located in the northwest part of the county. In 1882, Fred Taylor, pioneer archaeologist, dug into the mounds and discovered Indian remains.