Middle River is an unincorporated community and census-designated place in Baltimore County, Maryland, United States. The population was 25,191 at the 2010 census. A Middle River Train Station first appeared on the 1877 G.M. Hopkins & Co Baltimore County Map and by 1898 had a designated Post Office and modest street grid. The town expanded during the 1930s and 1940s and established the "Aero Acres" housing community which borders the railroad tracks and Martin Blvd. to serve as housing for people working at the Martin Aerospace Company. For this development, the architecture firm of Skidmore, Owings & Merrill designed gable-roofed Cape Cod houses with dimensions of 24 feet (7.3 m) by 28 feet (8.5 m), featuring large commercial-style windows in their principal rooms. In 1941 a total of 600 homes were built at Aero Acres using this design from Cemento (a cement/asbestos material).
Middle River is located at 39°20′2″N 76°26′26″W (39.333957, −76.440502).
According to the United States Census Bureau, the Census Designated Place (CDP) has a total area of 8.5 square miles (22 km2), of which 7.7 square miles (20 km2) is land and 0.7 square miles (1.8 km2), or 8.63%, is water.
At the 2000 census, there were 23,958 people, 9,425 households, and 6,399 families living in the CDP. The population density was 3,100.8 people per square mile (1,196.7/km²). There were 10,000 housing units at an average density of 1,294.3 per square mile (499.5/km²). The racial makeup of the CDP was 82.60% White, 13.21% African American, 0.60% Native American, 1.23% Asian, 0.03% Pacific Islander, 0.86% from other races, and 1.47% from two or more races.