Brentwood is an inner-ring suburb of St. Louis, located in St. Louis County, Missouri, United States. The population was 8,055 at the 2010 census.
Brentwood is located at 38°37′9″N 90°20′55″W (38.619102, -90.348715).
According to the United States Census Bureau, the city has a total area of 1.96 square miles (5.08 km2), all land.
The area that is Brentwood consists of three land purchases: that of Louis J. Bompart who acquired his lot first in 1804, that of the Gay family, and that of the Marshall family. In the 1870s, a man by the name of Thomas Madden arrived and soon became the businessman of the community. He operated a rock quarry, and constructed a tavern, a barbershop, a grocery store, and a blacksmith shop. Due to Madden's prominence in the community, the town was then named Maddenville.
With a location on the Manchester Trail, a route that was mostly frequented by mail coaches and prairie schooners going west, Maddenville in the 1800s became a prosperous town on the outskirts of St. Louis, to which it was connected by a streetcar line.
In 1919, it was discovered by the residents of Maddenville that the inhabitants of the neighboring Maplewood were planning to elect whether or not to annex their town.