The earliest electric railway, or streetcar line, in Northern Virginia opened in 1892. At their peak, when merged into a single interurban system (the Washington-Virginia Railway), the successors of this and several other lines ran between downtown Washington, D.C., Rosslyn and Arlington Junction – in present-day Crystal City – and out to Mount Vernon, Fairfax City and Nauck (in Arlington County). As a result, the trolleys mostly operated on private right-of-ways that their companies leased or owned. After they began operating, a number of communities developed along their routes.