Rock Port was laid out on Rock Creek in Missouri's fertile Glacial Plains in 1851 by Nathan Meek and succeeded Linden as the seat of Atchison County in 1856. Atchison County, organized in 1845 and named for U.S. Sen. David R. Atchison, lies in extreme northwest Missouri and is one of six counties formed from the Platte Indian Purchase annexed to Missouri in 1837. The county's north boundary remained unsettled until 1851, when the U.S. Supreme Court had the Missouri-Iowa boundary marked, and to the west the Missouri River channel separates the county from Nebraska; after the river changed course at one spot in 1867, the Supreme Court ruled in 1904 that the abandoned channel remained the boundary, giving land east of the river to Nebraska, and Missouri and Nebraska agreed in 1957 to reestablish the river boundary there. The Lewis and Clark Expedition camped along the Missouri in what is now Atchison County in 1804, Clark named the area Baldpated Prairie after the bare hills rising from the river plain, and Lewis explored the nearby Nishnabotna River, glossed as Indian for Canoe making, and called the country handsome. The area served by Rock Port was first settled by H. B. Roberts and Thomas Wilson in 1839, and nearby early settlements included a short-lived German Colony of 1846-47 directed by Cornelius Schubert. During the Civil War, Rock Port and Atchison County were at times subjected to guerrilla raids and troop movements. The county became a leader in corn production, and in 1950 was listed as having the highest valued farm land and buildings in Missouri. Prosperity was not assured until 1881, when two railroads were built through the county. Tarkio, the county's largest town, was laid out in 1880 by Charles Perkins on the Tarkio River, glossed as Indian for Walnut, and Tarkio College, identified as Presbyterian, was founded there in 1883-85. Rock Port was first incorporated in 1855 as Rockport, and that spelling has also been used. In the town stands the County World War I Memorial Building, and the Brownville Missouri River Bridge, built in 1940 between Missouri and Nebraska, is owned by the county. Among figures associated with county growth are Henry F. Stapel, a Rock Port editor and pioneer in the mutual insurance movement, and David Rankin, a noted farmer and pioneer in the settlement of Tarkio.