The 105 number was used twice: in the 1920s, as State Highway 105, and starting in 1932 as a route in Weston.
State Highway 105 followed today's Route 190 between US 5 in Enfield and Route 32 in Stafford Springs; in the late 1920s, this was extended to the Massachusetts state line in Union.
On Jan. 1, 1932, SH 105 was decommissioned, and split up between the original Route 15 and Route 20.
Commissioned in 1932, the not-so-old Route 105 (now Lyons Plain Rd) extended 3.59 miles north from Route 57 near the Merritt Parkway to the village of Lyons Plain in Weston. In 1963, this was turned over to the town. The road parallels present-day Route 136 about 1 mile to the north.
Jon Persky writes:
“...hang a right at Lyons Plain Rd and CT 57 - the first traffic light north of the interchange for the Merritt Parkway, exit 42 - and follow Lyons Plain to Valley Forge Road, which winds past the Saugatuck Reservoir ending at CT 53. Until the 1960s this was state route 105. Before the Depression depopulated the town of Weston, Lyons Plain and Valley Forge were full-fledged boroughs within the town. Today, the Lyons Plain area has some churches and a firehouse, but no commercial establishments; Valley Forge is completely underwater thanks to the Bridgeport Hydraulic Company and the creation of the Saugatuck Reservior. This route is also notable for some very interesting, and completely nonstandard, signage along Lyons Plain Rd past the Westport/Weston line. In addition to the history and the roadgeekiness, it's also an extremely pretty drive.”