Union is a city in Hardin County, Iowa, United States.

[5] According to the United States Census Bureau, the city has a total area of 0.55 square miles (1.42 km2), all land.

There were 188 housing units at an average density of 329.3 per square mile (127.1/km2).

Hispanic or Latino persons of any race comprised 3.5% of the population.

There were 200 housing units at an average density of 363.6 per square mile (140.4/km2).

34.9% of all households were made up of individuals, and 19.7% had someone living alone who was 65 years of age or older.

There were 209 housing units at an average density of 378.3 per square mile (146.1/km2).

29.5% of all households were made up of individuals, and 19.1% had someone living alone who was 65 years of age or older.

The Union-Whitten school district served Union until July 1, 1992, when it merged into BCLUW.