The Missouri River, created by geological glacial action thousands of years ago, historically served as a gateway to the West. First used by prehistoric Indians, it later served fur traders, explorers, and homesteaders. Among the earliest Europeans to use the river were the French, who competed with the Spanish and British for ownership of the area. After the United States bought the Louisiana Purchase from France in 1803, it began exploring its new territory. The Lewis and Clark Expedition passed here in 1804 on its way to the headwaters of the Missouri and eventually to the Pacific Ocean, returned in 1806, and camped nearby. The first steamboat to pass this way was the Western Engineer in 1819. After Nebraska Territory was established in 1854, steamboats hauled freight and passengers until railroads replaced them. A major railroad bridge constructed here by the Burlington in 1887 was replaced in 1977, and the highway bridge was completed in 1939. Today the Corps of Engineers maintains a 9-foot channel to Sioux City, and the river, railroads, and highways together serve this agricultural heartland of America.