Des Moines River, the largest river in Iowa, formed by the junction of two branches, known as the E. and TV. forks, which rise in a chain of small lakes in S. W. Minnesota, and flowing S. E. unite in Humboldt co., Iowa. From the junction it flows S. E. through the middle of the state, and joins the Mississippi at the S. E. corner, about 4 m. below Keokuk, having for a short distance formed the boundary between Iowa on the N. E. and Missouri on the S. TV. In its course of 300 m. the Des Moines drains 10,000 sq. m. in Iowa, passing through an undulating, fertile region, interspersed with tracts of prairie, rich in coal, and abounding in timber. There are many excellent mill sites along its banks. The fall from Fort Dodge, Webster co., to Ottumwa, Wapello co., is 2 ft. 4 in. per mile, and from Ottumwa to its mouth, 1 ft. 11 in. per mile. Many towns have sprung up along its banks, among which is Des Moines, the state capital. The principal tributaries from the west are the Raccoon, or Coon river, and North, Middle, and South rivers; the largest E. branch is the Boone, which rises in Kossuth and Hancock counties. Raccoon river rises in Buena Vista co., receives several tributaries, and empties into the Des Moines at the city of the same name.

An appropriation of lands to improve the navigation of the Des Moines was made by congress, but it was afterward diverted to the construction of the Des Moines Valley railroad. Before the diversion, however, a number of dams had been built in the lower part of the stream, which afford good water power.