After passing through a small strip of Charlestown on the east banks of the river, the route enters Everett, loses its expressway features and limited-access status, and becomes Broadway.

The route continues on through a short (0.25 miles (0.40 km)) corner of Melrose before entering Saugus.

The stretch south of the interchange to the Charlestown Bridge originally had no known route number assigned to it.

When it became designated as Route 99 circa 1971, its southern terminus was on the Charlestown Bridge, but this was moved to its present location following the Big Dig.

[citation needed] The Sweetser Circle has been the site of numerous major accidents, including a gas tanker rollover early on December 5, 2007 that resulted in 9,400 U.S. gallons (36 kL) spilling, igniting and destroying 21 vehicles and two large multi-family homes.