There have been several US 5A's in the state, all gone now:
Hartford North (Jan. 1, 1932 to Oct. 24, 1968)
The most well-known US 5A was long segment from Hartford to Agawam, Mass., now Route 159. The southern end was moved a few times; historical US 5A was usually a bit longer than Route 159 is today. In 1942, it extended 21.12 miles, from US 5 in Hartford to the state line. In 1944, possibly because US 5 had been relocated to the Charter Oak Bridge opening, US 5A now extended to the Berlin Turnpike in Wethersfield (using part of today's Route 314). This route followed Maple Avenue, Washington Street, Capitol Avenue, Trinity Avenue, High Street, and Main Street into Windsor. As the dike boulevard and North Meadows Expressway (today's I-91) were completed, US 5A was routed along those highways instead, then turning at today's Route 159 in Wilson.
In 1968, the state announced it was considering changing US 5A's designation to state route 159. In Massachusetts, the route would continue as MA 159. The reasoning:
- Since the new I-91 was the primary route north, US 5 was the alternate, and US 5A no longer merited a US route number
- The parallel US 5 and US 5A could lead to motorist confusion, especially along I-91, which crosses both routes multiple times
East Hartford North (1940 - 1945)
The lion's share of this route was Main Street in South Windsor, which was originally US 5 before the four-lane US 5 opened to the east.
Berlin (1940 - Mar. 29, 1963)
Worthington Ridge Road, formerly part of US 5.
Meriden - Wallingford (Jan. 1, 1932 - Mar. 29, 1963)
A 7-mile section including Old Colony Road.
New Haven I (Jan. 1, 1932 - 1940)
State Street south from today's Route 22; now part of US 5
New Haven II (c. 1950s - 1966)
Maple Avenue (today's Route 103) and Middletown Avenue (today's Route 17) from North Haven to New Haven; early US 5
Now only one US alternate route exists in the state: US 1A in Stonington.