NY 149 officially begins at exit 20 on the northbound Adirondack Northway (I-87) in the town of Queensbury, from where it follows a ramp eastward to US 9.

[7] While concurrent with US 9, NY 149 passes the Adirondack/Lake George Factory Outlet Mall and several other businesses located on both sides of the highway.

At the end of the factory outlets in the hamlet of French Mountain, NY 149 turns off US 9 and proceeds in a generally eastward direction toward the village of Fort Ann.

[11] East of this junction, the highway turns to the northeast and crosses the Blue Line into Adirondack Park ahead of an intersection with CR 7 (Bay Road).

[8] The first several miles of NY 149 in Washington County pass through isolated, rural areas as it curves to the north and south while following a generally east–west alignment.

Within the village, NY 149 passes the Fort Ann Cemetery and two blocks of homes before intersecting with US 4 at George Street.

While US 4 heads to the southeast, NY 149 continues due south, paralleling the Champlain Canal to an area known as Smith's Basin.

NY 149 continues generally northeastward through the town, passing through the isolated hamlet of Hillsdale before curving to the southeast toward South Granville.

The route proceeds through the village to its center, where NY 149 forks northeastward onto West Main Street and crosses over the Mettawee River.

[8] VT 149 heads southeastward away from the built up village of Granville into a more rural region of the Rutland County town of Pawlet, paralleling the Mettawee River as it progresses onward.

It heads past homes and through a dense forest as it intersects with Bull Frog Hollow Road just after the border.

After Bull Frog Hollow Road, the route proceeds eastward through an area dominated by quarries.

The portion of NY 149 that overlaps US 9 in Queensbury, designated as part of SH 417, was improved under the terms of a $82,700 (equivalent to $2.7 million in 2025) contract awarded on July 10, 1906.

[14][15] In 1913, construction began on the portion of what is now NY 149 in Granville south of North Street, internally designated as SH 5404.

The last portion of NY 149 with a known construction date is the section concurrent to US 4 in Fort Ann (part of SH 1224).

[24][25] It was extended again in the late 1950s to follow a pre-existing, unnumbered roadway west to US 9 in the Queensbury hamlet of French Mountain.

[5] On July 2, 2005, the Hadlock Pond Dam north of West Fort Ann failed, washing out four sections of NY 149 near that community.

Additionally, the state would also have to take a significant number of properties along the roadway in order to widen it, which would affect the character of the area.

After the first accident occurred at 3:10 a.m., a second tractor-trailer, who had stopped because of the tanker, rolled in reverse, jackknifing across the road and hitting a car.

[35] NY 149 between Martindale Road in the town of Queensbury and the Washington County line was upgraded by New York State Department of Transportation (NYSDOT) in the late 2000s.

The project consisted of repaving the roadway in areas, but also included widening the shoulder to 6 feet (1.8 m) wide, reconstructing and straightening NY 149 near Martindale Road along with a spot near the Queensbury Country Club.

Culverts would be replaced, drainage systems would be upgraded and they would create a new wetland mitigation area aside of NY 149.