It travels east southeast, crossing over Steele Brook, into the Oakville section of town.

Route 73 soon enters the city limits of Waterbury as Watertown Avenue, crossing over Steele Brook again.

Originally, Route 73 entered Waterbury on Watertown Avenue as it does today.

However, east of Windsor Street, instead of heading directly onto the Route 8 expressway, Route 73 continued to follow Watertown Avenue southeast to West Main Street then turned east along West Main Street to end at the intersection with Thomaston Avenue, which was the original alignment of Route 8.

However, no additional construction or right of way acquisition has taken place since then and the Route 73 freeway had been removed from the state's long range transportation plans since the mid-1970s.