McKeesport is a city in Allegheny County in the U.S. state of Pennsylvania; it is situated at the confluence of the Monongahela and Youghiogheny rivers and is part of the Pittsburgh metropolitan area. The population was 19,731 at the 2010 census. By population, it is Allegheny County's second-largest city, after Pittsburgh.Settled in 1795 and named in honor of John McKee, its founder, McKeesport remained a village until 1830 when coal mining began in the region. Large deposits of bituminous coal existed.McKeesport was incorporated as a borough in 1842 and as a city in 1891. Its population grew steadily until the mid-20th century, when it peaked in the 1940s. The city's population in 1900 was 34,227; in 1910, 42,694; in 1920, 45,975; and in 1940, 55,355. The decrease in the population since the 1940s is attributable to the general economic malaise that descended upon the region when the steelmaking industry moved elsewhere.