BY-PASS U.S. Federal Route 1 is a north-south highway in Southeastern New Hampshire. It runs completly with in Rockingham County, and the City of Portsmouth. It starts at U.S. Rt. 1, in Portsmouth, near Sagamore Creek Land. BY-PASS U.S. Rt. 1 then runs north to the Maine State Line. BY-PASS U.S. Rt. 1 passes through the following town in Rockingham County. Portsmouth BY-PASS U.S. Rt. 1 is not multi-plexed in Rockingham County. BY-PASS U.S. Rt. 1 intersects the following highways in Rockingham County. U.S. Rt. 1, at Portsmouth. New Hampshire State Route 33, at Portsmouth. U.S. Rt. 4, at Portsmouth. New Hampshire State Route 16, at Portsmouth. Spaulding Turnpike, at Portsmouth.