South Dakota’s western heritage is reflected here in eight skyward pillars whose framework merges in the form of a tipi, the Plains Indian home. The one-by-one-and-one-half-foot concrete lodge poles rise fifty-six feet and weigh six-and-one-half tons each, and their architectural style reflects the spartan lifestyle of the nomadic Lakota (Sioux) Nation. The Coteau des Prairie country to the south was among the first parts of South Dakota settled by the Lakota tribes. It was formed by the last great glacier that reached across South Dakota as far as the Missouri River, and as the ice melted, thousands of ground-out potholes became glacial lakes. To the southeast, Lake Traverse and Big Stone are remnants of a mighty river that drained ancient Lake Agassiz in Canada, and between them lies the continental divide separating waters flowing to Hudson’s Bay and to the Gulf of Mexico. Fur traders and voyageurs found this lake country prime trapping and trading territory and may have arrived as early as 1679. At that time the Santee Sioux—Wahpeton, Sisseton, Mdewakanton, and Wahpekute—were moving into the lakes region. Nearly two centuries later, in 1851, the Santee ceded this part of South Dakota to the United States in the Treaty of Traverse des Sioux. The U.S. Army established one of its earliest military posts in South Dakota in 1804 at Fort Sisseton, thirty-six miles southwest. The post was abandoned in 1889 and is now a South Dakota state park. Actual white settlement did not begin until the Sisseton-Wahpeton reservation area was opened in 1892.