CT 100 History
From 1963 to about 1970, Route 100 extended south to end at an extended Route 142. Scan from 1965 official state highway map.
In the 1920s, the state's internal highway numbers began with 101, so there was no state highway 100.
In 1932, the first Route 100 was created along what is now Route 39 between New Fairfield center (at Route 37) and Danbury center.
In 1934, the first Route 100 was decomissioned and divided up between an extended Route 39 (Ball Pond Rd and Milltown Rd into New York State) and a new Route 37A (the remainder of Ball Pond Rd and Clapboard Ridge Rd to Danbury).
In 1935, the modern Route 100 was commissioned in East Haven, from US 1 to Route 80, a length of 3.92 miles. In 1943 or 1944, it was extended south to Dodge Avenue, at the entrance to Tweed-New Haven airport, for a length of 4.69 miles.
Sometime in the 1950s, Route 100 was redefined to turn east at Main Street to end at Route 142.
In 1963, Route 142 was extended westward along today's Route 337 into New Haven. Route 100 was extended southward along Hemingway Ave. and Short Beach Rd. to end at Route 142.
In 1969, however, the state reversed its change to Route 142, leading to today's configuration for that road and Route 100.
In 1999, Route 100's intersection with Route 80 was relocated slightly, and Route 100's length decreased by 0.04 mile.