Marshall County, South Dakota, the last county organized east of the Missouri, was organized on May 2, 1885, after having been part of Sheyenne County in 1862, a gigantic Hanson in 1870, coincident with Stone in 1873, and the north half of Day in 1879, and it was created by the 1885 Legislature and named for Governor William W. Marshall of Minnesota. Its high coteaus and many wooded lakes made it an early habitat of the Cuthead Yanktonaise and Sisseton Sioux. White trappers and traders traveling from Lake Traverse to the Aricara villages on the Missouri near Grand River visited the area by 1800, and its first permanent resident was Joseph R. Brown in 1843, when he had a fur trade post at Buffalo Lakes near the southeast corner, later sold to the American Fur Company. In 1864, following the Santee Sioux outbreak in Minnesota, Fort Wadsworth was built near the county's south central border to restrain hostile Indians. It was a strongly entrenched post, was renamed Fort Sisseton in 1876, and was abandoned by the military in June 1889. Reconstructed in the 1930s, it became the most authentic old fort in the Midwest and in 1959 was named a state park. Nearby Roy Lake, with an extensive shoreline, is another state park. The county's first post office was established at Newark on June 15, 1883, with John F. Pulver as postmaster. The county became famous for fishing and upland game.