Early in the 20th century, the Pennsy tried electric power for its trains.
Its first effort was in the New York terminal area, where tunnels and a city law restricting the burning of coal precluded steam locomotives.
In 1910, the railroad began operating a direct current (DC) 650-volt system whose third-rail powered Pennsy locomotives (and LIRR passenger cars) used to enter Penn Station in New York City via the Hudson River tunnels.

The next area to be electrified was the Philadelphia terminal area, where Pennsy officials decided to use overhead lines to supply power to the suburban trains running out of Broad Street Station.
Unlike the New York terminal system, overhead wires would carry 11,000-volt 25-Hertz alternating current (AC) power, which became the standard for future installations.
In 1915, electrification of the line from Philadelphia to Paoli, Pennsylvania, was completed.
Other Philadelphia lines electrified were the Chestnut Hill Branch (1918), White Marsh (1924), West Chester (1928), the main line to Wilmington, Delaware, and in 1930 the Schuylkill Branch to Norristown, Pennsylvania, along with the rest of the main line to Trenton, New Jersey.

In 1928, PRR's president William Wallace Atterbury announced plans to electrify the lines between New York, Philadelphia, Washington, and Harrisburg.
In January 1933, through main-line service between New York and Philadelphia/Wilmington/Paoli was placed in operation.
The first test run of an electric train between Philadelphia and Washington occurred on January 28, 1935.
On February 1 the Congressional Limiteds in both directions were the first trains in regular electric operation between New York and Washington, drawn by the first of the GG1-type locomotives.

In 1934, the Pennsylvania received a $77 million loan from the New Deal's Public Works Administration To complete the electrification project begun in 1928, work was started January 27, 1937, on the main line from Paoli to Harrisburg; the low-grade freight line from Morrisville through Columbia to Enola Yard in Pennsylvania; the Port Road Branch from Perryville, Maryland, to Columbia; the Jamesburg Branch and Amboy Secondary freight line from Monmouth Junction to South Amboy; and the Landover-South End freight line from Landover, Maryland, through Washington to Potomac Yard in Alexandria, Virginia.
 In less than a year, on the following January 15, the first passenger train, the Metropolitan, went into operation over the newly electrified line from Philadelphia to Harrisburg.
On April 15, the electrified freight service from Harrisburg and Enola Yard east was inaugurated, thus completing the Pennsy's eastern seaboard electrification program.
The railroad had electrified 2,677 miles (4,308 km) of its track, representing 41% of the country's electrically operated standard railroad trackage.
Portions of the electrified trackage are still in use, owned and operated by Amtrak as the Northeast Corridor and Keystone Corridor high-speed rail routes, by SEPTA, and by NJ Transit.
Early in the 20th century, the Pennsy tried electric power for its trains. Its first effort was in the New York terminal area, where tunnels and a city law restricting the burning of coal precluded steam locomotives. In 1910, the railroad began operating a direct current (DC) 650-volt system whose third-rail powered Pennsy locomotives (and LIRR passenger cars) used to enter Penn Station in New York City via the Hudson River tunnels.
The next area to be electrified was the Philadelphia terminal area, where Pennsy officials decided to use overhead lines to supply power to the suburban trains running out of Broad Street Station. Unlike the New York terminal system, overhead wires would carry 11,000-volt 25-Hertz alternating current (AC) power, which became the standard for future installations. In 1915, electrification of the line from Philadelphia to Paoli, Pennsylvania, was completed. Other Philadelphia lines electrified were the Chestnut Hill Branch (1918), White Marsh (1924), West Chester (1928), the main line to Wilmington, Delaware, and in 1930 the Schuylkill Branch to Norristown, Pennsylvania, along with the rest of the main line to Trenton, New Jersey.
In 1928, PRR's president William Wallace Atterbury announced plans to electrify the lines between New York, Philadelphia, Washington, and Harrisburg. In January 1933, through main-line service between New York and Philadelphia/Wilmington/Paoli was placed in operation. The first test run of an electric train between Philadelphia and Washington occurred on January 28, 1935. On February 1 the Congressional Limiteds in both directions were the first trains in regular electric operation between New York and Washington, drawn by the first of the GG1-type locomotives.
In 1934, the Pennsylvania received a $77 million loan from the New Deal's Public Works Administration To complete the electrification project begun in 1928, work was started January 27, 1937, on the main line from Paoli to Harrisburg; the low-grade freight line from Morrisville through Columbia to Enola Yard in Pennsylvania; the Port Road Branch from Perryville, Maryland, to Columbia; the Jamesburg Branch and Amboy Secondary freight line from Monmouth Junction to South Amboy; and the Landover-South End freight line from Landover, Maryland, through Washington to Potomac Yard in Alexandria, Virginia.  In less than a year, on the following January 15, the first passenger train, the Metropolitan, went into operation over the newly electrified line from Philadelphia to Harrisburg. On April 15, the electrified freight service from Harrisburg and Enola Yard east was inaugurated, thus completing the Pennsy's eastern seaboard electrification program. The railroad had electrified 2,677 miles (4,308 km) of its track, representing 41% of the country's electrically operated standard railroad trackage. Portions of the electrified trackage are still in use, owned and operated by Amtrak as the Northeast Corridor and Keystone Corridor high-speed rail routes, by SEPTA, and by NJ Transit.
Pennsylvania Railroad