Route 122 originated as an alignment of U.S. Route 22, and a remnant of New Jersey State Route 28, which was designated in 1926 as part of the highway system as the Phillipsburg–Easton Bridge. The route continued as U.S. Route 22 until the completion of the bypass in 1938 around Phillipsburg, which US 22 was transferred to the bypass. The former alignment became U.S. Route 22 Alternate, lasting through the 1953 state highway renumbering. The route continued to run from the Phillipsburg–Easton Bridge to US 22, until 1993, when US 22 Alternate was decommissioned and replaced by Route 122 and County Route 678. The route was first named Chester Avenue, it was then named Route 29. In 1915, the New Jersey established its first highway department, thus, giving funding to localities to improve their roads. Later, it was renamed Route 22.
