It heads north along the eastern shore of Lake Waramaug and soon enters the town of Warren.

This western loop is an unsigned state highway known as Special Service Road 478.

It enters Cornwall after 2.5 miles (4.0 km), becoming Warren Hill Road.

[1][2] In 2010, the 0.50-mile segment of Route 45 running from the Junction with Route 202, through New Preston village, to the intersection with East Shore Road and Flirtation Avenue, also received state scenic designation.

The road from New Preston to Warren center, and continuing north up to the Housatonic River south of Cornwall Bridge, was designated as a state highway in 1922.