For many millennia, the Great Plains of North America were inhabited by nomadic Native Americans.

In 1802, Spain returned most of the land to France, but keeping title to about 7,500 square miles.

In 1803, most of the land for modern day Kansas was acquired by the United States from France as part of the 828,000 square mile Louisiana Purchase for 2.83 cents per acre.

In 1887, the Atchison, Topeka and Santa Fe Railway built a branch line from Neva (3 miles west of Strong City) to Superior, Nebraska.

This branch line connected Strong City, Neva, Rockland, Diamond Springs, Burdick, Lost Springs, Jacobs, Hope, Navarre, Enterprise, Abilene, Talmage, Manchester, Longford, Oak Hill, Miltonvale, Aurora, Huscher, Concordia, Kackley, Courtland, Webber, Superior.

In 2010, the Keystone-Cushing Pipeline (Phase II) was constructed north to south through Clay County, with much controversy over tax exemption and environmental concerns (if a leak ever occurs).

The solitary Democrat to win a majority of Clay County's votes has been William Jennings Bryan in 1896, although Woodrow Wilson in a four-way race in 1912, and Franklin D. Roosevelt in 1932 both obtained slim pluralities.

Roosevelt in 1936, when he lost to Kansan Alf Landon by eighty-four votes, remains the last Democrat to win forty percent of the county's vote, and Jimmy Carter in 1976 is the last to pass thirty percent.

† means a community is designated a Census-Designated Place (CDP) by the United States Census Bureau.

The city of Clay Center is considered governmentally independent and is excluded from the census figures for the townships.