Route 31 is a state highway in New Jersey, United States. It runs from U.S. Route 206/U.S. Route 1 Business (US 206/US 1 Bus.) in Trenton, Mercer County, north to an intersection with US 46 in the Buttzville section of White Township, Warren County. Along the way, Route 31 heads through the communities of Flemington, Clinton, and Washington. Most of the highway is state-maintained; however, the section within the city limits of Trenton is maintained by the city. Much of Route 31 is a two-lane highway that passes through farmland, woodland, and mountainous areas. Two portions of the route—from Trenton to Pennington and from Ringoes to Clinton—consist of more development.
The highway was constructed from 1926 to 1935. Route 31 has carried two different numbers in the past. It was known as Route 30 between 1927 and 1953, when it was renumbered to Route 69 to avoid conflicting with US 30 in southern New Jersey. It was renumbered to Route 31 in 1967 due to sign theft that resulted from the sexual meaning of the number 69. There were plans made in the late 1960s and early 1970s to build a freeway in the Route 31 corridor that would begin in the Trenton area and extend as far north as Interstate 84 (I-84) in Port Jervis, New York; however, it was canceled in the mid-1970s due to opposition from area residents and environmental and financial constraints. In recent years, the portion of Route 31 between Flemington and Clinton has been widened to four lanes. In addition, there was a failed project to build a bypass of Flemington that would have also eliminated the Flemington Circle.
Route description
thumb|left|View north along Route 31 at the border of Trenton and Ewing where state maintenance begins
Route 31 heads north from US 1 Bus./US 206 at the Trenton Battle Monument in Trenton, Mercer County, on city-maintained two-lane undivided Pennington Road. The route passes by residences and some businesses in the northern part of Trenton, crossing the intersection with Calhoun Street (CR 653). Route 31 enters Ewing and becomes state-mantainted at the point where it crosses the intersection with Parkway Avenue (County Route 634 [CR 634]). The route continues north through suburban residential areas and passes to the west of The College of New Jersey campus. The road continues north through farms, reaching commercial development as it approaches the Flemington area. The turnpike served as a connector along the old Hopewell Road from modern-day Lambertville (then called Georgetown) to New Brunswick. The road also served as a highly used connector route for the Jersey and Castenoga wagon lines, which served both of the aforementioned communities. The route from Trenton to Pennington was part of the Pennington Turnpike, another privately maintained pre-designation highway. The turnpike was chartered on March 17, 1854, by the General Assembly along an alignment of the old Pennington Road. The turnpike road was to be constructed no further than in breadth, and to be made out of stone, plank or gravel. The turnpike cost one cent for every carriage or sled pulled by horses or mules (and one cent more for every animal), five mills for horse and rider and every dozen of pigs and sheep. It cost two cents to move a dozen cattle, mules or horses. Fines were levied as high as $10 (equivalent to $ in ) to anyone who vandalized any structure along the turnpike. If the company did not construct their highway in six years, the state would then take over and make it a public highway. On November 1, 1898, the turnpike, made mostly of stone, was taken over by the state at a cost of $31,661.87 (equivalent to $ in ). Repairs were slated to be completed on the road by October 31, 1899. Also on March 17, 1854, the state legislature made the charter official for the Hopewell and Ewing Turnpike, which used the portion of Route 31 from Pennington to the current-day intersection with CR 654. The turnpike was taken over by the state in 1897 and the privately maintained company was dissolved.