Williamstown is an unincorporated community in Decatur and Rush counties, in the U.S. state of Indiana.

[3] An old variant name of the community was called Earl City.

[1] A post office was established at Williamstown in 1834, and remained in operation until it was discontinued in 1905.

[4] Williamstown is located at the boundary between Decatur and Rush counties.

This Rush County, Indiana location article is a stub.