In the mid-1930s, the city of Boston marked several alternate routes of Routes 1, 9, 28, and 37 that ran through the downtown area. Route C28 left mainline Route 28 by continuing north into Dorchester along Blue Hill Avenue instead of turning west onto Morton Street with Route 3. Just beyond the Franklin Zoo, C28 turned west along Seaver Street, continuing through Roxbury along Columbus Avenue. C28 then followed Columbus Avenue up to Charles Street at the Boston Common, turning north along Charles Street to Cambridge Street, then crossing the Charles River using the Longfellow Bridge. C28 met back with mainline Route 28 at Memorial Drive in Cambridge. In 1971, the Boston 'C' routes were retired and mainline Route 28 was relocated onto the former C28 alignment through downtown Boston. Route 28 was also later shifted to use its modern alignment along Embankment Road and the Charles River Dam Bridge.