The Maine Central Railroad was a U. S. class 1 railroad in central and southern Maine. It was chartered in 1856 and began operations in 1862. By 1884, Maine Central was the longest railroad in New England. Maine Central had expanded to 1,358 miles (2,185 km) when the United States Railroad Administration assumed control in 1917. The main line extended from South Portland, Maine, east to the Canada–United States border with New Brunswick, and a Mountain Division extended west from Portland to St. Johnsbury, Vermont, and north into Quebec. The main line was double track from South Portland to Royal Junction, where it split into a "lower road" through Brunswick and Augusta and a "back road" through Lewiston, which converged at Waterville into single track to Bangor and points east. Branch lines served the industrial center of Rumford, a resort hotel on Moosehead Lake and coastal communities from Bath to Eastport.

The Mountain Division is a railroad line that was once owned and operated by the Maine Central Railroad (MEC). It stretches from Portland, Maine on the Atlantic Ocean, through the Western Maine Mountains and White Mountains of New Hampshire, ending at St. Johnsbury, Vermont in the Northeast Kingdom. The line was abandoned in 1983 by MEC's successor, Guilford Transportation Industries (GTI). Guilford retained a stub between Portland and Westbrook. A section in New Hampshire remains in use by heritage railway Conway Scenic Railroad.