SR 4 begins at the New Hampshirestate line, where the roadway continues south as NH 4 towards Dover. From South Berwick, SR 4 runs in a northeasterly direction through the town of North Berwick, bypassing the center of Sanford to the east, and intersects US 202 in Alfred. SR 4 runs concurrently with US 202 for to the city of Auburn via the towns of Gorham, Windham and Gray. North of Auburn, SR 4 continues northward, staying near the west bank of the Androscoggin River, through the town of Turner, to Livermore, where it crosses the river to Livermore Falls. SR 4 continues to an intersection with US 2 in Wilton, and runs concurrently with it for to Farmington. SR 4 follows the Sandy River north of Farmington, through the towns of Strong and Phillips, and west to the river's source near Saddleback Mountain. The road turns north to Rangeley, where it turns west and runs concurrently with SR 16 at Oquossoc. SR 4 meets SR 17, then continues northwest to its terminus at Haines Landing on the shore of Mooselookmeguntic Lake.
History
SR 4 was designated in 1931 as a continuation of US 4 in New Hampshire, hence its number. Although US 4 does come close to the Maine border, the intended connection never came to fruition, as US 4 was routed south of Dover to terminate in Portsmouth. Instead, an indirect connection exists, facilitated by NH 4, NH 9, and NH 16. As first designated in 1931, SR 4 extended from its current southern terminus in South Berwick all the way to the Canada–US border. By 1937, most of the routes that are currently cosigned with it had been designated, most notably US 202. In 1946, SR 4 was truncated to its southern intersection with SR 16 in Rangeley, but was later re-extended along SR 16 to terminate at its current end at Haines Landing in 1951. Most of former SR 4 between SR 16 and the Canada–US border is now part of SR 27.
Junction list
Auxiliary routes
State Route 4A is the designation for two separate, but closely located, auxiliary routes of SR 4. While not directly connected to one another, they are linked by a stretch of US 202 and SR 4 between Hollis and Buxton.
Southern segment
The southern segment of SR 4A runs between the towns of Sanford and Alfred. It is concurrent over its entire length, running on sections of SR 109 and US 202. SR 4A is a service route for downtown Sanford, which SR 4 bypasses to the east. This segment of SR 4A begins at an intersection with SR 4 and SR 109 south of downtown. SR 4A and SR 109 run concurrently northwest into the center of town, where they intersect with US 202 and SR 11 at Lebanon and Winter Streets. SR 109 continues straight to join SR 11, while SR 4A turns onto Winter Street to join US 202. US 202 and SR 4A run concurrently to the northeast, crossing SR 224, then cross into Alfred where they intersect with SR 4 and SR 111. SR 4A ends at this intersection, US 202 turns north to join SR 4 and SR 111 begins to the east. ;Junction list
Northern segment
The northern segment of SR 4A runs for between Hollis and Buxton and is a northern alternate to US 202 / SR 4. Like the southern segment, this segment is signed north-south, but is oriented nearly due west to east. This segment begins at an intersection between US 202 / SR 4 and SR 35 in Hollis. SR 4A and SR 35 share a brief concurrency before SR 4A splits off to the east, crossing SR 117 in the process. The highway continues to the east into the town of Buxton. SR 4A then crosses SR 112 before terminating at US 202 / SR 4. ;Junction list Mileposts on this section of SR 4A continue from the southern segment, omitting the connecting section of US 202 / SR 4.
