[6] St. Clair was incorporated in 1907; the present name is in honor of General James St.

[1] According to the U.S. Census Bureau, the city has a total area of 0.82 square miles (2.12 km2), all land.

There were 313 housing units at an average density of 381.7 per square mile (147.4/km2).

20.1% of all households were made up of individuals, and 8.3% had someone living alone who was 65 years of age or older.

There were 305 housing units at an average density of 550.3 per square mile (212.5/km2).

62.4% were married couples living together, 7.5% had a female householder with no husband present, and 25.4% were non-families.

21.4% of all households were made up of individuals, and 10.2% had someone living alone who was 65 years of age or older.