Roberts County, South Dakota, long the home of the Sisseton, Wahpeton, and Cuthead Yanktonaise Sioux, became part of Deuel and Cheyenne Counties in 1862, with Deuel extending north to the 46th parallel in 1872. The reservation, extending south to Lake Kampeska in a giant flatiron, was established in 1867. Grant County included the part southeast of the reservation from 1873 to 1883, when Roberts County was created and named for S. G. Roberts, a Territorial Councilman of Fargo. It was organized on August 6, 1883, by Frederick Dittes, Charles Crissey, Indian Agent, and Reuben R. Hall, at Dittes’ residence, and Travare, 2 miles southwest of Browns Valley, was named county seat. In 1884 Wilmot won the election but, after losing two court actions, stole the records and was named county seat by the 1885 Legislature. Wilmot in turn lost an election in 1898 to Sisseton, which, fearing court action, likewise stole the records and again won approval in the 1900 election. White settlement on the reservation came in 1892, and the railroad reached Sisseton in 1893. Post offices included Sisseton Agency in 1872, Wilmot in 1881, White Rock in 1885, Corona in 1886, Summit, Sisseton, and Effington in 1892, and Rosholt, Victor, Hammer, and Claire City in 1914, when the Soo Line entered the county. Marshall County, South Dakota, the last county organized east of the Missouri, was organized on May 2, 1885; before that it had been in Sheyenne County in 1862, Hanson in 1870, 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 home 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 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 near the south central border was built to restrain hostile Indians. It was a strongly entrenched post, was renamed Fort Sisseton in 1876, was abandoned by the military in June 1889, was reconstructed in the 1930s, and in 1959 was named a state park. Nearby Roy Lake also became a state park. The county’s first post office was at Newark on June 15, 1883, with John E. Pulver as postmaster.