Route 110 connects Stratford to Monroe by way of Shelton, with distinct north-south and east-west segments (it's officially a north-south route in the state highway log). Other L-shaped routes include Route 22, Route 156, and Route 218.
In the 1920s, State Highway 110 followed the old main route from Hartford into Massachusetts along the west side of the Connecticut River:
In the late 1920s SH 110 was realigned to follow Route 159 all the way up.
The modern Route 110 was commissioned in 1932 as a 6.76-mile east-west route, from Route 111 in Monroe to Route 8 in Shelton. The north-south portion of today's Route 110, from Stratford to Shelton, was part of Route 8 (north of where Route 113 intersects now), and Route 8A (south of there to US 1). (For the first year or so, E. Main St (Route 8A) was part of US 1A.)
Part of modern Route 110 in Shelton near Nicholdale Farm was constructed in 1935.
In 1952, Route 8 was moved west and Route 110 extended south along the former Route 8 (Main Street). In 1963, the southernmost part of Route 110 was shifted to East Main Street (SR 708), and the leftover given to a shifted Route 113.
In 1958, the Route 15/110 interchange was upgraded from a 4-ramp partial cloverleaf to a 7-ramp nearly full cloverleaf, to handle increased traffic from nearby industrial sites (notably Sikorsky Aircraft). The cost was $721,000.
"Cool," you might be thinking, "let's go check this out." Well, you should have thought of that years ago. For safety reasons, the state removed two ramps around 1998.
A Route 110 freeway? Yes, if the Tri-State Transportation Commission had its way. The Commission in 1966 proposed a new east-west expressway through mid-Fairfield County, from Route 8 in Derby to US 7 in Ridgefield, then connecting with a proposed NY 35 expressway over the state line. The proposed but unbuilt expressway might also have carried the 34 or 35 numbering.
The TSTC instead called it the "Conn. 110 Expressway," citing its benefits as:
East-west route through the former Fairfield County. Fills 18-mile gap in regional highway grid. Connects rapidly developing suburbs. Extends stub-end expressway.
In 1969, the new Conn. 110 Expressway proposal surfaced in a dispute about a planned interchange at Florida Hill Road and the proposed US 7 freeway in Ridgefield. Residents nearly unanimously opposed the interchange at a town meeting, saying that 1) there were already two nearby interchanges proposed, at Route 102 and old US 7; and 2) this interchange looked like it was really in preparation for the Conn. 110 Expressway.
A DOT engineer replied that the Route 110 proposal was only "a line on a map", and that the state had no inclination to proceed with it—especially if residents did not want it. Furthermore, the Florida Hill Road interchange would be too small for crossing freeways; and the study line had Route 110 crossing US 7 to the south, at Route 102.
In 1975, the Regional Plan Association urged Connecticut not to proceed with its part of the plan. I haven't seen mention of reviving it since then.
Other than I-84 / US 6, Route 34, and the Merritt Parkway, no east-west routes serve Fairfield County between the shore and Danbury. It's easy to look at a map and see an extended Route 110 helping out, wending its way westward from Route 111 to Ridgefield... or at least the few miles to Route 25.
As it turns out, this idea is not original, and it's not even new.
In 1935, Special Act 272 was passed, directing the state to extend Route 110 about three miles westward, to intersect Route 25 at Route 59. In 1971, the idea was brought up again, as a project associated with the proposed Route 25 freeway in Monroe. During the intervening years, local officials repeatedly asked the state to proceed with the extension -- there's not even a town road going directly from one side of town to the other.
At the 1971 Route 25/110 hearing, a map of the proposed Route 110 extension was shown: a two-lane road from Route 111 at existing Route 110, westward to Route 25 at Route 59, going slightly north of Longview Road. This was never built, and might have been "collateral damage" from the cancelled Route 25 freeway.