Built as the Portland & Ogdensburg Railroad before acquisition by the Maine Central Railroad (MEC), the line initially provided transportation for summer visitors to grand Victorian hotels, including the Bay of Naples Inn in Naples (reached by connection with Sebago Lake steamboats), the Crawford House in Crawford Notch and the Mount Washington Hotel in Bretton Woods.

Cool, clean air at Sebago Lake and the White Mountains provided a refreshing escape from the heat, humidity and smoke of 19th-century cities.

The Flying Yankee train-set operated as the Mountaineer from Boston to Crawford Notch via Intervale Junction during World War II,[1] but passenger service had been reduced to a single daily round-trip between Portland and St. Johnsbury by the 1930s.

It saw relatively heavy through freight traffic from termination of the joint operating agreement with the Boston & Maine Railroad (B&M) in 1953 until abandonment in 1983, when GTI favored a B&M routing.

[6] Four or five diesel locomotives were typical head-end power for diesel-era freight trains; and a pair of EMD SW7s or non-dynamic-braked GP7s often provided helper service westbound.

[7] MEC's parent company, Pan Am Railways, retained ownership of the section of the line to Westbrook, which it operates as the "Mountain Branch."

This line was operated as the MEC Quebec Division until Maine Central terminated lease of the Hereford Railway in 1925.