Ottawa, city, seat (1864) of Franklin county, eastern Kansas, U.S. It lies on the Marais des Cygnes River. Ottawa was founded in 1864 near the Ottawa Indian Baptist Mission, which had been established in 1837 on lands given (1832) to the Ottawa Indians in exchange for their Ohio lands. During the Border War the area served as a centre of abolitionist activity; proslavery militia burned a portion of the mission in 1857. When the Indians were moved to Oklahoma in 1867, settlers rushed to the site; prosperity followed construction of railroad machine shops in 1872.
A handsome, tree-lined city, Ottawa is now the trading centre for a grain, poultry, and livestock area; manufactures include textiles and plastic and metal products. A natural-gas field discovered in 1907 remains in production. Pomona State Park is west of the city. Inc. 1866. Pop. (2000) 11,921; (2010) 12,649.