On June 7, 1854, the Bel-Del agreed to operate the Flemington Railroad and Transportation Company, where a connection was made with the Central Railroad of New Jersey (CNJ) at Flemington, New Jersey. LV coal trains began using the Bel-Del in January 1856, joining the Bel-Del by the LV's bridge over the Delaware River where it connected in Phillipsburg, New Jersey. An extension was then completed in 1864 that gave the Bel-Del access to the Delaware, Lackawanna & Western Railroad (DL&W) at Manunka Chunk, and permitted trains to operate via trackage rights to East Stroudsburg, Pennsylvania through the Delaware Water Gap. The Pennsylvania Railroad (PRR) began operating the Bel Del as the Belvidere Division of the United Railroads of New Jersey Grand Division in 1871 and purchased the line soon afterwards. The Flemington Railroad & Transportation Company then merged into the Bel-Del on February 16, 1885. For much of the late 19th century and early 20th century the railroad line proved vitally useful.