Rimmon Road, which carries Route 313 today, was once the Rimmon Falls Turnpike, which was chartered in May 1802. The original (1798) plan was to connect to the Derby Turnpike at Derby Landing, but instead the road went straight to New Haven from Seymour. It's not known when the turnpike was discontinued, but it survived beyond 1838.

In the 1920s, state highway 313 followed today's Route 30 between US 5 and Route 83.

The modern route 313 was commissioned in 1963. Most of it, from Old Ansonia Road in Seymour to Route 243, was formerly SR 563.

Route 313 freeway once planned

In the 1960s, the South Central Connecticut Planning Region proposed a freeway along Route 313, from the vicinity of a Route 10 freeway in New Haven to Route 8 in Seymour. Route 313, along with Route 34 and Route 17, would have served as a radial commuter route into New Haven.

Route 313 extension planned

In 2003, a Seymour construction company proposed extending Route 313 two miles northward, from Route 67 in Seymour to Route 42 in Beacon Falls. If extended, the road would run between Rimmon St. and Rimmon Hill Rd. to the west and Route 8 to the east. This would open up 230 acres -- one of the largest tracts left in town -- for light industrial use.

In March 2003, representatives of the construction company met with the Valley Council of Governments (COG), the local planning agency, to work toward getting approval from ConnDOT: they are interested in extending the route designation, not just the road.

In April 2003 the COG approved the conceptual plan: this doesn't mean construction can start, but makes it easier to apply for funds. In late 2003, the Valley COG identified the Route 313 extension as a candidate for future High Priority Project funding under the federal TEA-21 program. The project cost is listed as $3.5 million.

• "Firm wants to extend Route 313." New Haven Register, March 14, 2003.
• "Route 313 extension plan gets nod." New Haven Register, April 10, 2003.
• Valley Council of Governments. Regional Transportation Plan: Valley Region. Update 2003, February 2004.

• Route 313 Ends (Photos; Doug Kerr at state-ends.com)
• Route 313 - Google Maps