Mount Oliver is a borough in Allegheny County, Pennsylvania, United States. It is a largely residential area situated atop a crest about 3 miles (5 km) west of the Monongahela River. The borough is surrounded entirely by the city of Pittsburgh, having resisted annexations by the city, as it prefers to manage its own local needs and finances.
It is named for Oliver Ormsby, son of John Ormsby, who held the original land grant for the area from George III. Mount Oliver has experienced some tough times of late which are associated with the slippage of the steel-making capacity of the Pittsburgh region. The population was 3,403 at the 2010 census.
Mount Oliver is located at 40°24′41″N 79°59′12″W (40.411319, -79.986571).
According to the United States Census Bureau, the borough has a total area of 0.3 square miles (0.9 km²), all of it land.
Mount Oliver is completely surrounded by six Pittsburgh neighborhoods, including the South Side Slopes to the north, Arlington to the northeast, Mt. Oliver to the southeast, Carrick to the south, Knoxville to the west, and Allentown in the northwest corner.
As of the census of 2000, there were 3,970 people, 1,681 households, and 983 families residing in the borough. The population density was 11,720.0 people per square mile (4,508.3/km²). There were 1,864 housing units at an average density of 5,502.8 per square mile (2,116.7/km²). The racial makeup of the borough was 83.75% White, 11.74% African American, 0.23% Native American, 1.64% Asian, 0.03% Pacific Islander, 0.68% from other races, and 1.94% from two or more races.