By train
The Hackettstown Station is the furthest west that the NJ Transit trains go. There are trains to/from Hackettstwon throughout the day. It only goes directly to Hoboken, with connections at dover or newark to New York Penn Station
Martz Transit
(http://www.martztrailways.com/) has a stop in the Panther Valley Mall in Allamuchy, Exit 19 on Route 80, on some bus routes that travel from Northeastern Pennsylvania into New York City. The Main Street, Hackkettstown stop for the Martz bus was elinated in October 2008, due to economic concerns.
By car
Route 80 slices right though the Northern portion of Warren County, which is between the Delaware Water Gap to the West and Netcong to the East.
Route 78 will take you directly to Phillipsburg in the southernmost part of the county.