Monroe is a city located in east central Butler and west central Warren counties in the southwestern part of the U.S. state of Ohio. Monroe is a part of the Greater Cincinnati area.
Monroe was laid out in 1817 on the Dayton and Cincinnati pike. The city is named for President James Monroe, fifth President of the United States.
In the early 1830s, Monroe contained one store and 119 inhabitants.
Monroe is located at 39°26′41″N 84°21′51″W (39.444658, −84.364044).
According to the United States Census Bureau, the city has a total area of 15.89 square miles (41.15 km2), of which 15.87 square miles (41.10 km2) is land and 0.02 square miles (0.05 km2) is water.
As of the census of 2010, there were 12,442 people, 4,649 households, and 3,481 families living in the city. The population density was 784.0 inhabitants per square mile (302.7/km2). There were 4,896 housing units at an average density of 308.5 per square mile (119.1/km2). The racial makeup of the city was 92.6% White, 3.7% African American, 0.2% Native American, 1.7% Asian, 0.7% from other races, and 1.3% from two or more races. Hispanic or Latino of any race were 1.8% of the population.
There were 4,649 households, of which 39.2% had children under the age of 18 living with them, 61.6% were married couples living together, 8.8% had a female householder with no husband present, 4.5% had a male householder with no wife present, and 25.1% were non-families. 21.3% of all households were made up of individuals, and 10.1% had someone living alone who was 65 years of age or older.