Beginning in June 1903, the two single-track North River Tunnels were bored from the west under the Hudson River. A second set of four single-track tunnels were bored from the east under the East River, linking the new station to Queens and the Long Island Rail Road, which came under PRR control (see East River Tunnels), and Sunnyside Yard in Queens, where trains would be maintained and assembled. Electrification was initially 600 volts DC–third rail, and later changed to 11,000 volts AC–overhead catenary when electrification of PRR's mainline was extended to Washington, D.C., in the early 1930s.[12]
The tunnel technology was so innovative that in 1907 the PRR shipped an actual 23-foot (7.0 m) diameter section of the new East River Tunnels to the Jamestown Exposition in Norfolk, Virginia, to celebrate the 300th anniversary of the nearby founding of the colony at Jamestown. The same tube, with an inscription indicating that it had been displayed at the Exposition, was later installed under water and remains in use today. Construction was completed on the Hudson River tunnels on October 9, 1906, and on the East River tunnels on March 18, 1908. Meanwhile, ground was broken for Pennsylvania Station on May 1, 1904. By the time of its completion and the inauguration of regular through train service on November 27, 1910, the total project cost to the Pennsylvania Railroad for the station and associated tunnels was $114 million (about $2.7 billion in 2011 dollars), according to an Interstate Commerce Commission report.[16]:156–7