Mount Union is an unincorporated community and census-designated place (CDP) in Henry County, Iowa, United States.

According to the United States Census Bureau, in 2010 the city had an area of 0.11 square miles (0.28 km2), all land.

There were 52 housing units at an average density of 307.9 per square mile (118.9/km2).

There were 54 housing units at an average density of 490.9 per square mile (189.5/km2).

32.6% of all households were made up of individuals, and 9.4% had someone living alone who was 65 years of age or older.

There were 57 housing units at an average density of 513.2 per square mile (198.1/km2).

21.6% of all households were made up of individuals, and 3.9% had someone living alone who was 65 years of age or older.

There were 20.0% of families and 21.6% of the population living below the poverty line, including 6.8% of under eighteens and 25.0% of those over 64.