Linn County was one of the first 33 counties created by the Territorial Legislature and was organized on August 7, 1855, by R. E. Elliott; L. M. Love; Briscoe Travis; James P. Fox; Joseph D. Wilmot; James Driskill; William Rogers; and Elisha Tucker. It was named for Lewis Field Linn, a popular Senator from Missouri who played a prominent role in the acquisition of Oregon Territory, and contained the cities of Blue Mound, Parker, La Cygne, Mound City, Pleasanton and Prescott.
The Battle of Mine Creek, October 26, 1864, the Marais des Cygnes Massacre, May 19, 1858, and the Battle of Middle Creek, near Parker on August 25, 1856, when Texas Rangers from Fort Scott attempted to capture John Brown are all indicative of the turmoil in the county during the territorial period and are all significant to the county's early development.
The first church was opened by Jesuit missionaries for the Pottawatomie Indians near Centerville in 1838. The first fair was held on October 28, 1871, at Elm Grove. The first official county fair was held at Mound City in 1871. The school for Indians established near Centerville in 1838 was the first school. The first public school opened at Moneka, north of Mound City, on August 1, 1857.
The name of the Marais des Cygnes River supposedly derives from the legend of Evangeline and her search for her loved one Gabriel. She came to present Linn County in search of him. While there, Evangeline observed the tale of an Comanche Indian who wished to marry an Osage chief's daughter, but was forbidden to do so. When the man came to the village, the woman stepped into his canoe to leave with him, but upon reaching the middle of the stream, the canoe was pulled under the surface and in its place appeared two white swans. Evangeline, seeing this, exclaimed, "Ah, la Marais des Cygnes." (Source: Kansas State Historical Society)