 The modern subway in downtown Pittsburgh between Steel Plaza and First Avenue stations uses the Pittsburgh & Steubenville Extension Railroad Tunnel, which began construction in 1863.Rail lines (trolleys) had been a staple of the city and region since the late 19th century, the idea of a downtown to Oakland or East Liberty subway had been considered since at least the 1910s.A public referendum was passed to fund such a subway with an initial investment of $6 million on July 8, 1919, another $5.5 million subway plan was finalized at City Hall in meetings on March 28, 1932, and the public/private Allegheny Conference presented detailed plans and funding for a subway system on June 4, 1947.