After arrival at New York Penn Station, some trains load passengers and return to New Jersey, while others continue east to Sunnyside Yard for storage.

The Northeast Corridor Line is colored red on NJ Transit system maps and its symbol is the New Jersey State House.

In December 1855, work to extend the line's second track from Elizabethtown to Rahway was completed, eliminating the need for trains to meet in single-track territory.

[2] The New Jersey Railroad Board approved a contract for the rails for the second track between New Brunswick and Rahway to Cooper & Hewitt on February 5, 1859.

On November 5, 1882, the new PX interlocking tower was placed into service at Perth Amboy Junction in Rahway.

In 1915, the six tracking of the line between South Elizabeth and Colonia was completed, including grade separation work in Rahway and Linden.

[8] On September 25, 1929, the PRR Board authorized the extension of the line's fifth and sixth tracks between "LANE" and "ELMORA" interlockings.

[9] On April 15, 1930, the section of eastbound track 1 between Colonia station and St. George Street in Rahway was relocated to ground level.

On July 3, 1930, the PRR notified officials in Elizabeth that it would abandon plans to widen the line to six tracks between "LANE" and "ELMORA" as acquiring the condemnation award for the 30-foot wide strips was $290,828, when the railroad had estimated the cost would be $56,000.

[10] After overhead catenary lines were built between Trenton and Penn Station, it was possible to run trains of electric multiple units direct to Manhattan.

With the railroad unable to sustain the money losing commuter operation, let alone invest in improved physical plant and rolling stock, the New Jersey Department of Transportation became involved with maintaining the service.

After the Amtrak takeover of the Northeast Corridor the no-longer-hourly "Clocker" service was targeted at commuters making local stops bypassed by the high speed Metroliner and individually named trains.

The Clocker last ran on October 28, 2005, and thereafter NJ Transit began several extra Trenton-New York express trips.

With fast and frequent Amtrak and NJ Transit service, the Trenton to New York City portion of the Northeast Corridor is one of the busiest rail lines in North America.

[1] All service on the Northeast Corridor Line is electric via overhead lines and uses either Budd/GE Arrow III multiple unit cars during rush hours and normally one to two sets on the weekends, and push-pull locomotive trains hauled by ALP-46, an electric or ALP-45DP dual-mode locomotive, at all times.

In 2004 the River Line light rail Trenton station opened across the street, creating a rail link between the Northeast Corridor Line and Camden and the riverfront communities of Burlington County that did not require crossing the Delaware River into Pennsylvania.

Due to the popularity of the station with commuters arriving via Interstate from points south in New Jersey and Pennsylvania, a parking deck was added in 2007 with 2,066 more spaces for a total of 3,622.

[18] Hamilton Station did much to alleviate the increasingly desperate parking situations in Trenton and Princeton Junction.

Its direct freeway access and ample parking proved a hit with riders and it is one of the busiest stations on the New Jersey Transit system.

The conversion of the nearby American Standard factory into transit oriented development led to further ridership gains.

The Metropark rail station project was initiated by NJDOT in 1968 as part of a plan to accommodate businesses and commuters that were fleeing the old urban cores.

Opened in 2003, Secaucus Junction was built as a major transfer hub for the New Jersey Transit system.

[20] NJT currently originates trains to New York during peak hours from the Jersey Avenue station in New Brunswick.

As of 2013, the agency planned to build a flying junction and balloon loop called the Mid-Line Loop south of a new station south of Jersey Avenue in North Brunswick, allowing trains to turn around, enter and leave the Northeast Corridor without crossing over tracks.

[22] In January 2014, NJT awarded a $7.64-million design and engineering contract to develop a "train haven" and re-inspection facility where equipment could be stored during serious storms at an expanded and reconfigured County Yard in New Brunswick following severe flooding after Hurricane Sandy, which demonstrated the vulnerability of the agency's facilities to flooding.