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

[3] According to the United States Census Bureau, the city has a total area of 0.29 square miles (0.75 km2), all land.

There were 52 housing units at an average density of 174.2 per square mile (67.3/km2).

There were 48 housing units at an average density of 165.5 per square mile (63.9/km2).

23.8% of all households were made up of individuals, and 9.5% had someone living alone who was 65 years of age or older.

There were 50 housing units at an average density of 173.6 per square mile (67.0/km2).

34.0% of all households were made up of individuals, and 8.5% had someone living alone who was 65 years of age or older.

There were 27.0% of families and 42.9% of the population living below the poverty line, including 56.8% of under eighteens and 23.8% of those over 64.