The Millstone and New Brunswick Railroad (M&NB) was chartered in the mid-19th century as a seven-mile long branch line from New Brunswick, New Jersey to East Millstone, New Jersey. Construction was completed and the line began operation on December 19, 1854.
In 1871, under the order of the company's president Martin Howell, the M&NB signed a 999-year lease with the United Jersey Railroad Company, which would later become part of the Pennsylvania Railroad known as the Millstone Branch. In 1915, the company was dissolved and became part of the United Jersey Railroad Company.
The M&NB was originally intended to cross the Millstone River and connect to western points in 1874 via the ill-fated Mercer and Somerset Railway, which was a short-lived line of the Pennsylvania Railroad in western New Jersey.
The Mercer and Somerset Railway ran from Somerset Junction on the Belvidere Delaware Rail Road via Pennington and Hopewell to Millstone, with an intended connection to the Millstone and New Brunswick Railroad, via a bridge across the Millstone River, for a through route to New Brunswick.
The Mercer and Somerset Railway was abandoned in 1880 after filing for bankruptcy, and the connection over the Millstone River to the M&NB was never built, except for a stone pillar in the middle of the Millstone River that remains today.
The Millstone Branch boasted 12 passenger trains a day from East Millstone to New York City. Passenger stations, which were merely small wooden shacks, were located at East Millstone, South Middlebush Road, Clyde Road, Voorhees (now Route 27), and Jersey Avenue. Passenger service permitted Millstone residents easy access to New Brunswick for shopping on weekends and allowed New York City businessmen the opportunity to commute. With the advent of the automobile, all passenger service ended in 1930. After that year the track past Route 27 (Voorhees) was only used sporadically by a local freight train to access the rubber factory in East Millstone; track became weed covered and maintenance deferred. The stations at Clyde and Voorhees were abandoned on June 8, 1932. The last passenger station to survive was Middlebush, which was razed in 1948.