Montgomery County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 535,153, making it the fifth-most populous county in Ohio. The county seat is Dayton. The county was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada.

Montgomery County is part of the Dayton, Ohio Metropolitan Statistical Area.

Geography

According to the U.S. Census Bureau, the county has a total area of 464 square miles (1,200 km²), of which 462 square miles (1,200 km²) is land and 2.8 square miles (7.3 km²) (0.6%) is water.

Demographics

As of the 2010 United States Census, there were 535,153 people, 223,943 households, and 138,060 families residing in the county. The population density was 1,159.5 inhabitants per square mile (447.7/km²). There were 254,775 housing units at an average density of 552.0 per square mile (213.1/km²). The racial makeup of the county was 73.9% white, 20.9% black or African American, 1.7% Asian, 0.2% American Indian, 0.8% from other races, and 2.4% from two or more races. Those of Hispanic or Latino origin made up 2.3% of the population. In terms of ancestry, 24.9% were German, 12.8% were Irish, 9.7% were American, and 8.8% were English.

Of the 223,943 households, 29.7% had children under the age of 18 living with them, 41.6% were married couples living together, 15.3% had a female householder with no husband present, 38.4% were non-families, and 32.2% of all households were made up of individuals. The average household size was 2.33, and the average family size was 2.94. The median age was 39.2 years.