Seward County is a county of the U.S. state of Kansas. Its county seat and largest city is Liberal. As of the 2020 census, the county population was 21,964. The county was formed on March 20, 1873, and named after William Seward, a politician and Secretary of State under Abraham Lincoln and Andrew Johnson.

For millennia, the Great Plains of North America were inhabited by nomadic Native Americans. From the 16th century to the mid-19th century, the region that became southwestern Kansas was part of the vast hunting grounds utilized by tribes such as the Pawnee, Osage, Comanche, and Wichita. Following the Louisiana Purchase of 1803, early United States government expeditions explored the territory, frequently documenting the landscape as an arid expanse that became known as the "Great American Desert", which delayed early permanent Euro-American settlement.

In 1854, the Kansas Territory was organized, then in 1861 Kansas became the 34th U.S. state. During the Bleeding Kansas era (1854–1861), the violent ideological and political conflicts over slavery were concentrated almost entirely in the eastern half of the territory; the unorganized geographic area that would eventually become Seward County remained completely unsettled by Euro-Americans, devoid of permanent voting populations, and entirely unaffected by the guerrilla warfare, raids, or electoral fraud occurring along the Missouri border.

In 1873, Seward County was established, although it was administered from one of several neighboring counties until the county commissioners of Finney County organized Seward County as a municipal township of Finney County on June 10, 1885, with the temporary seat of government at Sunset City. The township was divided into two voting precincts - one headquartered at Sunset City and the other at Fargo Springs. The county was organized on June 17, 1886, with Governor John A. Martin designating Springfield the county seat and appointing men from Fargo Springs as county officers as not to favor one town over the other. Rivalry between Fargo Springs and Springfield became so intense both towns sent armed bodies of men to the other to prevent their voters from reaching the polls, causing a disputed election in 1885.

The county seat dispute was finally settled when the railroads bypassed both Fargo Springs and Springfield in favor of an alignment through southern Seward County, spurring the rapid growth of Liberal, which won the final election for county seat in on December 8, 1892, by 125 votes.

In the early 20th century, agricultural production shifted as Liberal briefly became a major market for broom corn, shipping hundreds of railcars of the crop annually. By 1910, hard winter wheat replaced broom corn as the primary regional cash crop.

The town of Arkalon, established in 1888 along the Cimarron River, served as a local railroad shipping hub for two decades. In 1914, a major flood destroyed the Cimarron River bridge leading into the settlement. Following the bridge failure, the Chicago, Rock Island and Pacific Railroad rerouted its regional operations through Liberal, which caused Arkalon to be abandoned; its post office closed in 1929.

The local economy shifted further from an exclusively agrarian base following the discovery of the Hugoton Gas Field in 1920. Subsequent drilling operations established the county as a major source of natural gas production.