In the 1920s, State Highway 145 was the number for the old Ousatonic Turnpike, much of which is now abandoned, on the northeast bank of the Housatonic River. The road went from Shelton to New Milford.

The modern Route 145 was commissioned in 1932. This is a strange one. In 1938, the state highway commissioner wrote: "Intersection of Old Clinton Road and Grove Beach Rd, Westbrook, Clinton, Westbrook to intersection with Route 80, Saybrook."

The 1942 highway log describes the route as "from 3-way junction Conn. 145 in Westbrook clockwise to Jct. Conn. 144, Saybrook (now Deep River)".

What does this mean? Here's the route, all 10.86 miles of it, from, er, 12 o'clock onward:

• Grove Beach Rd., heading south, across US 1 (this was assigned in 1935)
• continue west, following the shore, to Shore Rd.
• Shore Rd. to Beach Park Rd.
• Beach Park Rd., going north now, back across US 1
• short overlap southbound on US 1
• Old Post Rd. (part of today's Route 145) northeast, to Grove Beach Rd., which is the other leg of Route 145. This is the 3-way intersection with itself.
• Old Clinton Rd. (part of today's Route 145)
• Horse Hill Rd. (still part of today's Route 145)
• Old Horse Hill Road (a former alignment; the new road to the east opened around 1968)
• Cross Rd.
• Winthrop Rd. and Westbrook Rd., to end at Bushy Hill Road, the old Route 144

What about the roads that make up modern-day Route 145? From Cross Road northerly, they diverged:

• Stevenstown Road was a town road until 1935 (became SR 621; later, 145)
• Cedar Lake Road (Deep River) was also a town road until 1963 (became part of Route 145)
• Winthrop Road (Chester) was a town road until 1939 (became SR 432; later, 145)

In 1939, Winthrop Road in Chester, from the Deep River town line to Route 148, was added to the state highway system as SR 432.

In 1943 or 1944, Routes 144 and 145 were moved slightly, with Route 145 continuing to Route 80 along Stevenstown Road, now extending 11.47 miles.

In 1963, Route 145 was extended to Route 148, and the portion south of US 1 was deleted. The southeasterly leg became unsigned SR 625.

In 1959, there is a notation of "cancelled unimproved section" and "extended to Deep River town line". This might be the Cross Road / Winthrop Road / Westbrook Road section.

In 1972, there is a notation of "abandoned section of old Route 145" in Westbrook, without details; this may be the Old Horse Hill Road section.