Monroe City is a town in Harrison Township, Knox County, Indiana, United States. The population was 545 at the 2010 census.
Monroe City was named for one of its founders, Monroe Alton.
Monroe City is located at 38°36′57″N 87°21′19″W (38.615891, -87.355232).
According to the 2010 census, Monroe City has a total area of 0.27 square miles (0.70 km2), all land.
As of the census of 2010, there were 545 people, 217 households, and 153 families residing in the town. The population density was 2,018.5 inhabitants per square mile (779.3/km2). There were 238 housing units at an average density of 881.5 per square mile (340.3/km2). The racial makeup of the town was 98.7% White, 0.6% African American, 0.2% Native American, and 0.6% from other races. Hispanic or Latino of any race were 0.7% of the population.
There were 217 households of which 37.8% had children under the age of 18 living with them, 53.0% were married couples living together, 14.3% had a female householder with no husband present, 3.2% had a male householder with no wife present, and 29.5% were non-families. 29.0% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.08.