It ran west for 28.45 miles (45.79 km) from Port Morris Junction in Port Morris, New Jersey, near the south end of Lake Hopatcong about 45 miles (72 km) west-northwest of New York City, to Slateford Junction in Slateford, Pennsylvania near the Delaware Water Gap.

It was 11 miles (18 km) shorter than the Lackawanna Old Road, the rail line it superseded; it had a much gentler ruling gradient (0.55% vs. 1.1%); and it had 42 fewer curves, with all but one of those remaining permitting passenger train speeds of 70 mph (110 km/h) or more.

[3] The construction of the roadbed required the movement of millions of tons of fill material using techniques similar to those used on the Panama Canal.

Conrail ceased operation of the Cut-Off in January 1979, removed the track in 1984, and sold the right-of-way to private developers.

[4] The 39-mile (63 km) route (later known as the "Old Road" after the New Jersey Cut-Off opened) had numerous curves that restricted trains to 50 mph (80 km/h).

Although Truesdale recognized early on that the Old Road needed to be replaced, it really wasn't until after 1905 that the railroad was in a position to take up the project in earnest.

This led Truesdale to authorize teams of surveyors to map out potential replacement routes westward from Port Morris, New Jersey, to the Delaware River for what would be the railroad's largest project up until that time.

The amount of work per mile varied; the largest share apparently went to David W. Flickwir, whose Section 3 included Roseville Tunnel and the eastern half of the Pequest Fill.

To accommodate the labor gangs, deserted farmhouses were converted to barracks, with tent camps providing additional shelter.

These workers were viewed with suspicion by the local populace in Warren and Sussex counties, with the town of Blairstown going as far as hiring a watchman at $40 per month for the duration of the project.

With several thousand men working on the project for over three years, the area all along the Cut-Off, and as far west as Portland, Pennsylvania, benefitted financially.

In 1910, for example, five workers were killed in a single blasting mishap near Port Morris, one of several deadly accidents that involved dynamite.

[2] Depending on the fill size, material was dumped from trains that backed out onto track on wooden trestles or suspended on cables between steel towers.

[14] Contractor David W. Flickwir, whose section included Roseville Tunnel and the eastern half of the Pequest Fill, worked around the clock during the summer of 1911 when construction fell behind schedule.

In recognition of this, a detector fence was installed west of Roseville Tunnel in 1950 to change trackside signals to red if rocks fell.

Early in the 20th century, the DL&W's woman in white, Phoebe Snow, was featured in a poster that touted the new line and the Pequest Fill.

The Lackawanna Limited was also modernized and renamed the Phoebe Snow, helping breathe freshness back into a passenger train program that had seen only modest improvements since the 1930s.

Besides cutting travel time, the Cut-Off required fewer engines to pull eastbound freights up to the summit at Port Morris.

Initially, no speed limit existed on the Cut-Off, with engineers (both freight and passenger) being expected to exercise "good judgment".

By 1943, 131-pound-per-yard (65 kg/m) rail had been installed on the Cut-Off,[23] which permitted fast freights to run at 60 mph (97 km/h) through the Erie Lackawanna years.

But Conrail eventually shifted all freight traffic to other routes, citing the grades over the Pocono Mountains and EL's early-1960s severing of the Boonton Branch near Paterson, New Jersey.

Conrail ran its final through freights via the Cut-Off on November 16, 1978, and used it to move a light engine from Croxton Yard to Scranton two days later.

An Amtrak inspection train ran on November 13 of that year, and counties in New Jersey and Pennsylvania made attempts to acquire the line.

Nevertheless, Conrail removed the tracks on the Cut-Off in 1984, and in the following year sold the right-of-way to two land developers: Jerry Turco and Burton Goldmeier.

Subsequent federal studies conducted on the Cut-Off and the mainline into Pennsylvania found a need to restore passenger service.

In 2011, after a nearly three-decade effort to reactivate the line, NJ Transit launched the $61 million Lackawanna Cut-Off Restoration Project.