Scranton is a city in the northeastern part ofPennsylvania, United States. It is the county seat of Lackawanna County and the largest principal city in the Scranton/Wilkes-Barre metropolitan area. Scranton had a population of 76,089 in 2010, according to the U.S. Census, making it Pennsylvania's sixth-most-populous city after Philadelphia, Pittsburgh, Allentown, Erie, and Reading. Scranton is the geographic and cultural center of the Lackawanna River valley, and the largest of the former anthracite coal mining communities in a contiguous quilt-work that also includes Wilkes-Barre, Pittston, and Carbondale. Scranton was incorporated as a borough on February 14, 1856, and as a city on April 23, 1866. Scranton became known as the Electric City when electric lights were introduced at Dickson Locomotive Works in 1880. Six years later, the nation's first successful, continuously operating electrified streetcars began operating in the city. Residents of Scranton are referred to as "Scrantonians".