The RVRR located its Watnong depot on the northern bank of the Whippany River on the east side of Lake Valley Road. On a rail profile map the "final" 7 miles from Mendham to Watnong (2 miles from Morristown) appears as a gently downhill ride into the county seat of Morris County, New Jersey. Built as the Rockaway Valley Morristown Extension Railroad, the first train arrived in Watnong in early August 1892. Of all the sections of RVRR right-of-way, this would prove to be the most problematic, as the last several miles into Watnong traversed a swamp. For most railroads this would have required that extra fill material and ballast be placed in order to build up the right-of-way well above the surrounding water table. But the RVRR constructed the section through Washington Valley (near Milepost 22), very much like every other section on the railroad. The result: this section, particularly during wet periods, would almost literally sink into the muck.