Route 37 was commissioned in 1932, with a few changes since then. Before 1932, it was known as State Highway 136. In 1922, a portion of SH 136 (future Route 37) north of Coburn Road was shifted eastward in Sherman.

Old Route 37 near New Fairfield center is evidence of a slight rerouting in the past; I don't have details of when this took place.

In Danbury, Route 37 originally started at White Street, which was US 6 at the time, and included a segment of Main Street that is now the northernmost part of Route 53. Its southern end was moved north in 1962, shortly after the I-84 freeway opened, when US 6 was moved to overlap with I-84.

The Sherman Center Bypass proposal

Heading northbound toward Sherman Center, Route 37 undergoes a sharp turn to the right before intersecting Route 39, and both routes continue to the center of town. In 1978, the town's Plan of Development included a proposal for a Route 37 bypass, which would both eliminate the sharp curve and decrease thru traffic in the center.

The first phase would carry Route 37 on 3,300 feet of new alignment to meet Route 39 north of the Town Hall. A spur would connect the bypass to the town center, intersecting Route 37/39 south of Sawmill Road. Another phase, with 1,900 feet of new construction, would continue the bypass to end at Route 37 with Holiday Point Road.

However, the bypass was never formally studied. In 1990, ConnDOT stated that traffic projections for the next 20 years did not warrant building the bypass. By 2001, the project was no longer in the town's Master Plan.

Widening proposed in 1990s

The Housatonic Valley Council of Elected Officials (HVCEO) recommended widening Route 37 to four lanes for a short distance, from the vicinity of its start at Route 53 to Jeannette Road. A 1996 traffic study recommended the widening, and in 1999 the city council approved a motion to apply for a $6 million grant (state and federal money) for the project. Some turning lanes would be added, and traffic signals upgraded.