Immediately east of the bridge, it meets the southern end of Route 17A, which leads to Portland center.

It then enters Columbia, intersecting Route 87 before reaching a junction with US 6 at the western end of the Willimantic bypass.

Route 66 turns east as a collector of local traffic headed for Willimantic.

[1] From US 6 in Columbia to the end in Windham, Route 66 is designated the Grand Army of the Republic Highway.

The entire length of modern Route 66 was originally improved in the 19th century as various private turnpikes.

From East Hampton via Marlborough to the Hebron-Columbia line, the road was the Hebron and Middle Haddam Turnpike that was chartered in 1802.

The section from I-84 in Southington to US 6 in Columbia was renumbered as Route 66, including the newly opened freeway segment.