- Southern Terminus:
- Longfellow Bridge (MA 3) in Cambridge
- Northern Terminus:
- Massachusetts-New Hampshire state line
- 35.51 miles
US 3 is a north/south route in Massachusetts and New Hampshire. It begins at the Longfellow Bridge (MA 3) in Cambridge. The first section is Memorial Drive, a highway along the Charles River through Cambridge with a combination of traffic lights and grade-separated interchanges. Memorial Drive ends at Gerry's Landing Road. From this point, US 3 is routed along local streets to the north until it reaches I-95. It is multiplexed along I-95 for a short distance. It then splits off and runs north as an expressway to the Massachusetts-New Hampshire state line.