In 1927, Route 42 was legislated to run along the Black Horse Pike, a road that traces its origins back to 1855. In that year, the Camden and Blackwoodstown Turnpike Company was established by entrepreneurs who had helped create the White Horse Pike to build a gravel road that would run from Camden south to Blackwoodtown and eventually to Atlantic City, from Ferry Avenue in Camden to Route 48 (now U.S. Route 40) in McKee City. By 1941, U.S. Route 322 was assigned to follow the routing of Route 42 between Williamstown and McKee City. With the 1953 New Jersey state highway renumbering, which eliminated long concurrencies between U.S. Routes and State Routes, the southern terminus of Route 42 was cut back to Williamstown to avoid the concurrency with U.S. Route 322.