What is now US 206 was part of several trails used by
Lenape Native Americans: the Shamong Trail, later known as the Cape May Road, ran from what is now
Crosswicks to
Cape May; a trail running from Trenton through Crosswicks; the
Assunpink Trail, later known as the Old Dutch Road, running from Trenton north to
New Brunswick; and the Great Minisink Trail, running from Navesink through
Netcong to Minisink Village in modern-day Montague Township. In 1801, the Morris Turnpike was legislated to run from
Elizabeth through Netcong to
Culver's Gap. In 1804, the Union Turnpike was chartered to run from Morristown to the crossing at Dingman's Ferry in Montague Township. In 1814, the
Deckerton and Newton Turnpike branched from Newton through Deckerton, now
Sussex, to
New York. The Crosswicks and Trenton Turnpike was chartered in 1854; the road is now locally known as Broad Street, and was included in US 206 west of White Horse. Prior to 1927, what is now US 206 in New Jersey was legislated as part of several routes. Between Bordentown and Trenton, the current alignment was designated as a part of
pre-1927 Route 2 in 1916. Between Trenton and Princeton, present-day US 206 became the southernmost part of
pre-1927 Route 13 in 1917. In 1921, the current route from Princeton north to Bedminster Township was legislated as part of
pre-1927 Route 16. After the
United States Numbered Highway System was created in 1926, the route between Bordentown and Trenton became the northernmost part of US 130 while it became a part of US 1 between Trenton and Princeton. In the
1927 New Jersey state highway renumbering, several state highways were legislated along present-day US 206.
Route 39 followed the route from Hammonton to White Horse, while
Route 37 was designated along it between White Horse and Trenton. From Trenton north to Princeton, pre-1927 Route 13 was replaced by Route 27. Present-day US 206 between Princeton and Newton became part of Route 31, a route that was to go past Newton to the New York border near
Unionville, while the portion north of Newton to the Delaware River in Montague became Route S31, a spur of Route 31. Another spur of Route 31,
Route 31A, was legislated in 1941 to run from Route 31 in Princeton to
Route 33 in
Hightstown; only a small portion of this was built over the Northeast Corridor railroad line and is now
Route 64. In 1938, US 206/Route 31 was designated to bypass Somerville, the former alignment was known as
Route 177 from the 1960s until 1974. In the 1940s, US 206/Route 39 was realigned to the south of White Horse; the former alignment was known as
Route 160 between the 1960s and the 1980s. Also in the 1940s, the northern terminus of US 206 was moved to its current location at US 209 in Dingman Township, Pennsylvania. In the
1953 New Jersey state highway renumbering, the state highways running concurrently with US 206 were removed. When US 206's current alignment bypassing Columbus was built by the 1960s, the designation of
Route 170 was given to the old alignment through Columbus; this road was turned over to Burlington County in the 1980s and is now CR 690. On April 24, 1954, the Greater Philadelphia-Delaware-South Jersey Council released a proposal for a
freeway system in the
Philadelphia area that included an extension of the Trenton Freeway from US 206 south of the border between Burlington and Mercer counties north to the center of Trenton. In the late 1960s, a freeway was proposed for the US 206/Route 54 corridor, running from US 30 in Hammonton south to
Route 55 and the proposed
Route 60 near
Vineland and
Millville. Originally, a
parkway had been planned in 1932 to serve the US 206 corridor between Hammonton and Trenton, but never materialized. The freeway between Vineland/Millville and Hammonton was to cost $47 million and was intended to provide a better route between the two areas than the existing two-lane roads. However, it was never built due to environmental and financial issues. A freeway was also proposed for US 206 in northwestern New Jersey during the 1960s. In 1964, a Route 94 freeway was planned to follow US 206 between Netcong and Newton on its way to the proposed
Route 23 freeway in
Hamburg. The Tri-State Transportation Commission proposed a longer US 206 freeway that was to connect I-78 and I-287 in Bedminster Township north to Newton, incorporating the southern portion of the Route 94 proposal. This freeway was intended to relieve traffic on existing roads and provide access to recreation areas. By the late 1960s, the US 206 freeway would be planned by NJDOT to connect I-80 in Netcong north to Montague. In 2002, NJDOT modified plans for the bypass. The bypass is to be mostly four lanes wide and run to the east of Hillsborough, with the southernmost portion only being two lanes; one interchange was planned with CR 514. The road is to meet a Smart Growth goal by preserving land and eliminating two planned interchanges that would have increased congestion. In July 2009, it was announced that construction of the US 206 Hillsborough bypass, which is projected to cost $148 million, would start in 2010. This section is currently designated US 206 Bypass. In early 2015, work on grading and utility relocation for the ends of the bypass was slated to be completed. Work on constructing the northern and southern ends of the US 206 bypass of Hillsborough was originally planned to begin in early 2017. On April 13, 2018, construction began on the final phase to build the northern and southern ends of the bypass. The final phase of the Hillsborough bypass, which is projected to cost $36.6 million and be funded through state and federal money, opened on June 5, 2021. The Hillsborough Bypass is named for
Peter J. Biondi, a former assemblyman and Hillsborough mayor who died in 2011. The project was slated to be finished in November 2013. NJDOT is planning on widening the route in Hillsborough to four lanes and adding a concrete median from Doctors Way to Brown Avenue, where the four lane highway south of the Raritan River ends. This will replace the railroad overpass that is primarily blocking the widening project. The first half, from Doctors Way to Valley Road, was to start in the middle of 2020 and was anticipated to be completed by late 2022. The second half, from Valley Road to Brown Avenue was to take place in 2022 and take two years to complete. == Major intersections ==