Origins and assignment In 1911, the
New York State Legislature created Route 43, an unsigned
legislative route extending from the southern village line of
Stillwater to the western village line of
Schuylerville via the
hamlet of Quaker Springs. On March 1, 1921, Route 43 was renumbered to Route 44 to eliminate numerical duplication with another legislative Route 43 in
Western New York. At the same time, Route 44 was extended southwest from Stillwater to
Clifton Park via
Mechanicville and west from Schuylerville to
Saratoga Springs. The first set of posted routes in New York were assigned in 1924. Two of the routes assigned at this time were
NY 6, a north–south route extending from the
New York City line to the
Canada–United States border, and
NY 30, another north–south route connecting NY 6 in Mechanicville to the
Vermont state line west of
Fair Haven. NY 6 left
Albany on modern
NY 32 and followed it to Mechanicville, where NY 6 veered westward on what is now
NY 67 and NY 30 picked up the current alignment of NY 32. NY 30 continued north on modern NY 32 to
Glens Falls, at which point it went east to
Hudson Falls via Warren and River streets. It headed northward from there to Vermont on modern US 4. From Mechanicville to Schuylerville, NY 30 utilized the alignment of legislative Route 44. By 1926, NY 30 was rerouted north of
Whitehall to continue north toward the Canadian border. The old alignment of NY 30 between Whitehall and Vermont was not assigned a new number. Meanwhile, an alternate route of NY 6 on the east side of the
Hudson River between
NY 5 (now
US 20) in
East Greenbush and NY 6 in
Waterford was designated as NY 6B by 1926. In the original plans for the
U.S. Numbered Highway System, the north–south highway along the western bank of the Hudson River was designated as
US 9 while the highway on the eastern bank was assigned
US 109. The two routes were concurrent from Albany to Mechanicville, where US 9 went west to follow NY 6 while US 109 continued north on NY 30. The designations met again south of Glens Falls, where US 109 ended at US 9. Also in the original plans was US 4, which was assigned to all of NY 30's original alignment between Glens Falls and the Vermont state line. In the final system alignment approved on November 11, 1926, the routing of US 9 was altered to follow its modern alignment between Albany and Glens Falls while US 109 was reconfigured to use NY 6B between East Greenbush and Waterford.
Southward extension and overlaps When U.S. Routes were first posted in New York in 1927, US 9 was restored to its originally planned alignment between Albany and Glens Falls (via Waterford and Mechanicville) while the US 109 designation went unassigned. The portion of US 109's alignment south of Waterford became
US 9E instead. US 4 was assigned as planned in 1926,
overlapping NY 30 between Glens Falls and Whitehall. The NY 6 designation was completely removed at this time. In the
1930 renumbering of state highways in New York, US 9 was realigned to follow its modern routing between Albany and
Round Lake. The portion of US 9's former routing between Waterford and Mechanicville as well as all of US 9E north of US 20 became a southward extension of US 4, which left its original alignment in Hudson Falls and followed a previously unnumbered riverside highway south to
Northumberland. In between Northumberland and Mechanicville, it utilized the former routing of NY 30, which was reassigned to
another highway as part of the renumbering. Virtually all of US 4 south of Hudson Falls initially overlapped other routes, all of which were assigned as part of the renumbering. In between Hudson Falls and Northumberland, US 4 overlapped
NY 32B, which began in Glens Falls and followed US 4's former routing east to Hudson Falls. From Northumberland to
Schuylerville and from Bemis Heights to Waterford, US 4 was part of
NY 32. The segment from Schuylerville to Bemis Heights was designated
NY 32A. Lastly, the part of US 4 south of Northern Drive (then-
NY 40) in
Troy was concurrent to NY 40. By 1932, NY 40 was rerouted through Troy to follow a more easterly alignment through the city. The realignment moved the northern end of the overlap southward to the junction of US 4 and Winter Street in
North Greenbush. Most of the overlaps were eliminated as time went on. In the early 1940s, NY 32A was reassigned to
another highway in the
Catskill Mountains while NY 32B was truncated to end in Hudson Falls. The former routing of NY 32A became a realignment of NY 32, creating an uninterrupted overlap between US 4 and NY 32 from Waterford to Northumberland. In the mid-1950s, work began on a project to upgrade a preexisting riverside highway between Bemis Heights and Schuylerville. The project was completed by 1958, at which time the roadway became part of a realigned US 4. The overlap with NY 40 was eliminated in the late 1950s when NY 40 was truncated to begin at the junction of US 4 and Winter Street. ==Major intersections==