July 29: The CNJ's Jersey City extension opens, from about Spring Street in Elizabeth to the Jersey City terminal, including a long bridge across Newark Bay.
February 22: The New Jersey Railroad (PRR) builds a new bridge over the Passaic River, cutting the distance through Newark and Harrison. Some passenger trains continue to use the old alignment, the Centre Street Branch.
December 2: A frog war begins between the Erie and DL&W at the west end of the Erie's tunnel where the new Boonton Branch would join.
December 14: The DL&W begins running passenger trains on its Boonton Branch.
January 9: The frog war between the Erie and DL&W ends, with the frog being placed to allow DL&W Boonton Branch trains to run through the Erie's tunnel.
1872
August 23: Trains are first to run along the Erie's Newark and Hudson Railroad from Newark through their tunnel to Jersey City.
1873
The Pennsylvania Railroad constructs a new passenger ferry terminal with 12 tracks and six platforms. The wooden terminal is built on piers over the water.[3]
The Hudson Connecting Railway, part of the New Jersey Midland and later NYS&W, completed to West End Junction with Erie connection to Marion Junction.
1877
May 12: The DL&W opens its new tunnel through the Palisades, ending its trackage rights through the Erie's tunnel. Included with the tunnel are western approaches to the DL&W mainline and Boonton Branch; the former includes a new bridge over the Hackensack River, south of the old one (which is then used only for the Erie's Newark and Greenwood Lake Branches). The new alignment at first crosses the New Jersey Midland Railroad (NYS&W) at grade.