The community is located four miles west of New Prague at the junction of State Highway 19 (MN 19), County Road 31 (201st Avenue), and Church Avenue. Nearby places also include Heidelberg, Henderson, and Belle Plaine. The West Branch of Raven Stream flows through the community.
Union Hill is located within Derrynane Township in Le Sueur County; and also located within Belle Plaine Township in Scott County. A post office previously operated in the community from 1876 to 1903. Union Hill is located within ZIP code 56071 based in New Prague.
The community is present primarily due to the 1867 founding of St. John the Evangelist (Roman Catholic) Church.