In 1963, the Erie Main Line south of Paterson to its connection with the Bergen County Line at Carlton Hill in East Rutherford was abandoned and service began using the former Lackawanna Boonton Line south of Paterson via Lyndhurst and the Upper Hack Lift bridge as the route through downtown Passaic was abandoned. Boonton Line service began using the Erie's Greenwood Lake division up to its junction the Lackawanna Boonton Line at Mountain View in Wayne as the old Lackawanna right-of-way in Paterson was used for the construction of Interstate 80. The Erie Jersey City terminal was abandoned by 1956 and all Erie service now used the Lackawanna Hoboken Terminal.
Service under Erie Lackawanna introduced new GE U34CH diesels and Comet I cars in 1970 which lasted under NJ DOT and Conrail into the NJ Transit era. Metro-North began responsiblity for service north of Suffern in 1983. Service was increased along with the opening of the Secaucus Transfer Station in late 2003.
After the transfer station, the Main Line runs through an industrial section of Secaucus. Shortly afterwards the Bergen Line separates off on the new routing. The Main Line then crosses over the Hackensack River on the single-track Upper Hack Lift bridge, built in 1958.
The one track continues for a brief distance until it once again becomes two, under the New Jersey Turnpike's western spur. The train continues through the Meadowlands and passes the first grade crossing at Valley Brook Avenue in Lyndhurst. The line curves slightly and passes under the 1903 Kingsland tunnel. Kingsland station is shortly after the tunnel and is in an open cut. Just beyond Kingsland station is Lyndhurst station, located on an embankment.
The Main Line passes under U.S. Route 46 and the Garden State Parkway before it crosses under and over several streets in south Paterson. This portion of the line was single-tracked, then double-tracked in a rehabilitation project in 2002. The line passes under Interstate 80 and heads into downtown Paterson. Paterson station is elevated, with a center platform.
Continuing north, the Main Line is on an elevated grade through Paterson, passing over streets. After several grade crossings in an industrial area, the tracks crosses over the Passaic River on a truss bridge. Hawthorne is the next stop, at grade level. After a long stretch, the train reaches Glen Rock station, at grade level at a crossing.
After Glen Rock station, Ridgewood Junction is reached. This is where Main Line will merge with the Bergen County Line. The line widens to three tracks. Ridgewood station is next, with Spanish-style design on the station building and platforms.
Next is Ho-Ho-Kus, also at grade. Waldwick follows with an abandoned station building on the northbound side and a footbridge connecting the two platforms. Waldwick Yard is just north of the station, and just following Waldwick Yard is a grade crossing. North of the grade crossing (which has three tracks) the line becomes two tracks.
Mahwah follows and is the last station in New Jersey. Crossing over the New York state line, the train arrives at Suffern, the last stop. Some trains continue past to Port Jervis. The yards are located just to the north, under the New York State Thruway overpass.
All trains on the Main Line are push-pulled by diesel locomotives. Coaches used are from the Comet series, and often feature Metro-North owned Comet Vs as these are pooled with New Jersey Transit's coaches as part of the operating agreement.