In the 1920s, State Highway 137 followed today's Route 101 between modern-day Route 169 and Route 12.

Commissioned in 1932, the modern Route 137 formerly entered Stamford center via Summer St. south of Route 104, but as of 1976 takes Washington Blvd.

Its number matches New York's route at the state line, which was designated in 1930.

However, late 1931 plans in Connecticut called for Route 137 to be called Route 27, to fit a pattern with 29 and 33 in the southwest (and probably 23 and 31). As route number continuity at the border was useful for motorists, Connecticut decided to use an extension of New York's established number 137.

In 1959, the state allocated $2.2 million to widen High Ridge Road (Route 137 between Route 104 and the Merritt Parkway) from two lanes to four lanes.

On June 28, 1962, a four-mile section from Long Ridge Road to the Merritt Parkway was dedicated the Yankee Division Highway, honoring New England's 26th Division which served in World Wars I and II.

Tentative freeway proposal, 1960s

There were a few area proposals for a north-south highway between Stamford and Pound Ridge, N. Y. or Bedford, N. Y. In 1956, the Westchester Planning Department proposed a high-speed "Stamford - Bedford Village Road" between Routes 104 and 137, though noting that the route "might be cancelled."

In 1962, the Tri-State Transportation Committee proposed an arterial upgrade: four lanes divided with a median, no access control, from I-95 to the Merritt Parkway. This did get implemented along the Washington Boulevard segment in 1976.

In 1969, Westchester county proposed upgrading Route 137 to a freeway, from NY 172 south. Route 137 would have had interchanges at Route 15, Route 104, US 1, and I-95. This plan was not adopted and is now inactive.