[3] The first county seat was Calliope in 1860, then a small village with 15 inhabitants, and now part of Hawarden.

In June 1902, the construction began on a new Sioux County courthouse designed by W.W. Beach.

From 1976 until 1982 the building was completely restored, and in 1977, it was listed on the National Register of Historic Places.

Eastern Sioux County drains to the south east to the Floyd River.

22.20% of all households were made up of individuals, and 11.40% had someone living alone who was 65 years of age or older.

[14] As of 2011[update], 80% of the county residents belong to major denominational churches, compared to 36% of the total U.S.

[14] Sioux County is the home to two four-year liberal arts colleges; Northwestern College in Orange City and Dordt University in Sioux Center.

Due to its religious Dutch Reformed character, Sioux County is overwhelmingly Republican in Presidential elections.

[19] In the six elections since then, the Republican candidates has never received less than 75 percent of the county's vote.

[20] It is located in what was, until 2013, Iowa's 5th congressional district which had a Cook Partisan Voting Index of R+9 and was represented by Republican Steve King.

[22] The population ranking of the following table is based on the 2020 census of Sioux County.