[2] It is located approximately 15 miles (24 km) west of the Illinois-Indiana state line on U.S. Route 24.

[3] Incorporated in 1865, the name "Watseka" derives from the Potawatomi name "Watch-e-kee", "Daughter of the Evening Star", the wife of early eastern Illinois settler Gurdon Saltonstall Hubbard.

[4] The Old Iroquois County Courthouse was constructed in 1866, with two additions built in 1881 and 1927.

The petitions were approved by the County Board of Supervisors, and the Old Courthouse re-opened as a museum that same year.

According to the 2021 census gazetteer files, Watseka has a total area of 2.94 square miles (7.61 km2), all land.

36.33% of all households were made up of individuals, and 17.83% had someone living alone who was 65 years of age or older.