Lackawanna County is a county in the Commonwealth of Pennsylvania. It is located in Northeastern Pennsylvania and had a population of 215,615. Its county seat and most populous city is Scranton. The county was created on August 13, 1878, following decades of trying to gain its independence from Luzerne County. Lackawanna was Pennsylvania's last county to be created, and the only county to be created after the American Civil War. It is named for the Lackawanna River.