Interstate 691 branches east from I-84 along the Cheshire and Southington town line along a rural course to Crow Hollow along the Hanging Hills. Passing south of Cathole Mountain, the freeway enters the urban area of Meriden and continues north of the city center. I-691 connects with Route 15 (Wilbur Cross Parkway), Interstate 91 and Route 66 west of Higby Mountain. Route 66 east extends the freeway north of Beseck Mountain into the town of Middlefield.
Interstate 691 began as a freeway for U.S. 6A between Exits 8 and 13 in 1965. By 1969, the designation shifted from U.S. 6A to Connecticut Route 66, with construction extending the road west to Exit 4 by 1970. Interstate 691 was established by the American Association of State Highway and Transportation Officials ( AASHTO) along with I-284 in Hartford on July 13, 1976. I-691 however was not signed until 1987, one year prior to the completion of its connection to Interstate 84.1