In the 1937 renumbering of Monmouth County roads, numbers 1 through 5 were reserved for the longer, "cross-county" routes; those numbered 6 and above were to be more local in nature. County Route 1 was designated to run from the Mercer County line via Freehold and Eatontown to the Long Branch city limits. With the establishment of the 500 Series of county routes, CR 1 was superseded by CR 524 from the Mercer County line to Smithburg, and CR 537 from Smithburg to the Long Branch boundary. The present CR 1 was formed when part of CR 3 was separated from the balance of CR 3 with the 1952 establishment of CR 527 as part of the 500 Series routes. Since the CR 1 designation was available, that portion of CR 3 between CR 527 and CR 571 was re-designated as County Route 1.
In addition to those listed below, the following 500-series county routes serve Monmouth County: