U.S. Route 5A (Connecticut)

Route 159
Map of northern Connecticut with CT 159 highlighted in solid red and of southern Massachusetts with MA 159 highlighted in dotted red
Route information
Length:	21.14 mi (34.02 km) Connecticut: 16.82 mi Massachusetts: 4.32 mi
Existed:	1968 – present
Major junctions
South end:	Main Street (near I-91) at the Hartford-Windsor town line
	I-291 in Windsor, CT I-91 in Windsor Locks, CT Route 57 in Agawam, MA
North end:	Route 75 / Route 147 in Agawam, MA
Location
Counties:	CT: Hartford, MA: Hampden
Highway system
Routes in Connecticut Interstate U.S. State SSR SR ← Route 157 Route 160 → ← Route 152 MA Route 168 → ← US 5 US 5A (CT) US 6 → ← US 5 US 5A (MA) US 6 →

Route 159 is a state highway connecting the Hartford and Springfield areas in the U.S. states of Connecticut and Massachusetts. It begins as the northern extension of Main Street in Hartford and proceeds northward along the west bank of the Connecticut River towards Agawam, Massachusetts. The route ends at the junction of Route 147 and Route 75 in Agawam center just south of the West Springfield city line. The route was originally designated as U.S. Route 5A in 1932 and was renumbered to its modern designation in 1968.

Route 159 officially begins at the Hartford-Windsor town line as Windsor Avenue, near an interchange with I-91. In Windsor, it underpasses I-291, with access to and from the east provided by Deerfield Road. Almost immediately, it meets the eastern end of Route 218. After passing the east end of Route 178, Route 159 enters the center of Windsor, passing the town green before intersecting the southern end of Route 75. It then crosses the Farmington River, and starts to parallel the west bank of the Connecticut River, which it will for most of the rest of its length. In Windsor Locks, it meets I-91 once again at Exit 42, and has a brief overlap with Route 140. It passes along the eastern side of Suffield, where it has a brief overlap with Route 190. It then crosses the Massachusetts state line into Agawam, where it passes by Six Flags New England before entering the center of town. North of the center, Route 159 signage ends at an interchange with Route 57, but the official route continues north along Main Street to the intersection of Route 75 and Route 147 just south of the Westfield River and the West Springfield city line.