In the 1920s, State Highway 339 started at W. Main St. in Waterbury, west of where it crosses Route 8 today, and followed Watertown Ave. into Watertown. The street name changed to Main St. at the town line, and SH 339 followed it to end at SH 350 (today's US 6).
Route 73 was commissioned from part of SH 339, ending at the new Route 63, which continued northward to US 6. By the late 1920s, Chase Parkway had replaced W. Main St. as the main route west out of Waterbury, and Route 73 started at Route 8 instead of US 6. Its original alignment was close to today's:
- W. Main St, from Thomaston Ave. (at that time, Route 8) to Watertown Ave.
- Watertown Ave. to the Watertown line (merges with present-day Route 73)
- Main St. to Route 63 (same as present-day route)
In the 1960s, the Route 8 freeway was being constructed in the area, and it appears provisions were made for a proposed Route 73 freeway (see below) connecting it to central Watertown. On Sept. 20, 1965, a segment of Route 8 from W. Main St to Huntington Ave. opened, and Route 73 was relocated to a short four-lane divided section of road ending in a partial freeway interchange at Route 8. The leftover portion of Watertown Ave. and W. Main St. remained in the state system, but as unposted SR 846.
Route 73 westbound leaves Route 8 on a dual-lane left exit, built in anticipation (I presume) of a planned 73 freeway. The overpass carries Route 8 southbound. Today, Route 73 narrows to two lanes after 0.85 miles. Photo by Jim K. Georges.
The above photo is a popular scene. Steve Anderson's Route 73 page uses Jim's photo as well (long before this page did), and Doug Kerr took his own photo for State-ends.com at nearly the same point.
I haven't found much information about the state's freeway plans for Route 73, but the 1965 opening of the Route 8 interchange and stretch of four-lane alignment leading to Aurora St. implies that it had been contemplated since the early 1960s.
By 1969, the the Tri-State Transportation Commission proposed a Route 73 freeway; Connecticut's Expressway Test Plan did as well. The freeway would have ended at Route 63 or continued to US 6, both in Watertown. The proposal would have connected Route 8 to Route 63 or US 6 in Watertown. By 1975, however, Route 73 was off the state's short and long-range plans.