New Hampshire Route 123 (abbreviated NH 123) is a 63.055-mile-long (101.477 km) secondary north–south state highway in southwestern New Hampshire. The southern terminus of the route is at the Massachusetts state line in Mason where, as Mason Road, the road continues as an unnumbered local road in the town of Townsend. The northern terminus, as signed, is at the Connecticut River, where the highway continues west for 0.313 miles (0.504 km) to U.S. Route 5 in Westminster, Vermont, as Vermont Route 123 (VT 123). Route logs, however, place the terminus at New Hampshire Route 12 in Walpole.

Quick Facts Route 123, Route information ...

Route 123
Map of southern New Hampshire with NH 123 highlighted in red
Route information
Maintained by NHDOT
Length	63.055 mi[1] (101.477 km)
Major junctions
South end	Mason Road in Townsend, MA
Major intersections	NH 31 in Greenville US 202 / NH 101 in Peterborough NH 9 in Stoddard NH 10 in Marlow NH 12 in Walpole
North end	VT 123 near Walpole
Location
Country	United States
State	New Hampshire
Counties	Hillsborough, Cheshire, Sullivan
Highway system
New Hampshire Highway System Interstate US State Turnpikes
← NH 122 → NH 124
← VT 122 VT → VT 125

Close

In Walpole, NH 123 runs in a wrong-way concurrency with NH 12 north–south alongside the Connecticut River, the water body that represents the border between New Hampshire and Vermont. For the entire length of the NH 12/NH 123 concurrency, NH 123 South is, in reality, heading north on the compass while NH 123 North is traveling to the south.

In October 2005, heavy flooding in the New Hampshire area forced the closure of NH 123 in two different locations. The first was at the intersection of NH 123 and Cold River Road near Drewsville, where a bridge was destroyed from high water in the Cold River, approximately 5 miles (8 km) east of North Walpole. The second closure was approximately 3 miles (5 km) south of the junction with New Hampshire Route 123A in the town of Alstead, where a section of roadway was completely washed away by the water. Both sections were subsequently rebuilt and reopened.

New Hampshire Route 123A (abbreviated NH 123A) is a designation held by two separate state highways in New Hampshire, United States. Although the two segments are not directly connected, they are linked by their parent route, New Hampshire Route 123.