| State: | MA |
| Type: | MA |
| Route: | 1A |
| Map Custom: | yes |
| Length Mi: | 95.120 |
| Length Ref: | [1] |
| Length Round: | 2 |
| Established: | By 1927 |
| Direction A: | South |
| Direction B: | North |
| Terminus A: | in Pawtucket, RI |
| Junction: | in Attleboro in Wrentham in Dedham in Boston in Boston in Beverly from Newburyport to Salisbury |
| Terminus B: | in Seabrook, NH |
| Previous Type: | US |
| Previous Route: | 1 |
| Next Type: | MA |
| Next Route: | C1 |
Route 1A is a north - south state highway in Massachusetts, United States. It is an alternate route to U.S. 1 with three signed sections and two unsigned sections where the highway is concurrent with its parent. Due to the reconfiguration of tunnel interchanges brought on by the completion of the Big Dig, Route 1A is discontinuous in the downtown Boston area. Vehicles entering Downtown Boston via the Sumner Tunnel must take I-93 north to the exit for Government Center and make a U-turn to access the entrance ramp to I-93 south (which silently carries Route 1A south as well) and vice versa.[2]
A short segment of Route 1A, 1.8miles in length, in Attleboro runs from U.S. Route 1A at the Rhode Island border through a junction with Interstate 95, before heading north and merging with Route 1. The entire length of this segment is known as Newport Avenue.
This segment of Route 1A extends roughly north from North Attleborough to Dedham, passing through the towns of Plainville, Wrentham, Norfolk, Walpole, Norwood and Westwood on the way. Prior to its realignment along I-95 and I-93, Route 1 continued north along the Providence Highway towards Boston at the junction of Route 1A and that road.