Sunnyside Yard is a large coach yard, a railroad yard for passenger cars, in Sunnyside, Queens

Sunnyside, Queens

Sunnyside is a neighborhood in the western portion of the New York City borough of Queens, in New York state, in the United States. It shares borders with Hunters Point and Long Island City to the west, Astoria to the north, Woodside to the east and Maspeth to the south...

 in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

.
The yard is owned by Amtrak

Amtrak

The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...

 and is also used by New Jersey Transit

New Jersey Transit

The New Jersey Transit Corporation is a statewide public transportation system serving the United States state of New Jersey, and New York, Orange, and Rockland counties in New York State...

. The shared tracks of the Long Island Rail Road

Long Island Rail Road

The Long Island Rail Road or LIRR is a commuter rail system serving the length of Long Island, New York. It is the busiest commuter railroad in North America, serving about 81.5 million passengers each year. Established in 1834 and having operated continuously since then, it is the oldest US...

 (LIRR) Main Line

Main Line (Long Island Rail Road)

The Main Line is a rail line owned and operated by the Long Island Rail Road in the U.S. state of New York. It begins in Long Island City and runs along the middle of Long Island about 95 miles to Greenport...

 and Amtrak's Northeast Corridor

Northeast Corridor

The Northeast Corridor is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities...

 pass along the southern edge of the yard. Northeast of the yard a balloon track

Balloon loop

A balloon loop or turning loop allows a rail vehicle or train to reverse direction without having to shunt or even stop. Balloon loops can be useful for passenger trains and unit freight trains, such as coal trains....

 (or reverse loop) is used for "U-turning" Amtrak and NJ Transit trains which terminate at Penn Station. Leading eastward near the south side of the yard, this balloon track switches off and turns left under the LIRR/Amtrak tracks, turns left once again, and merges with the Sunnyside yard track to turn the train west toward Penn Station.
The Pennsylvania Railroad

Pennsylvania Railroad

The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....

 (PRR) completed construction of the yard in 1910.