Branch lines served the industrial center of Rumford, a resort hotel on Moosehead Lake and coastal communities from Bath to Eastport.

The MEC established rail service to the Penobscot Bay in 1871 by leasing (for fifty years) the then just-completed 33-mile (53 km) of track built by the Belfast and Moosehead Lake Railroad (B&ML).

The B&ML's grade ran the length of Waldo County from the port town of Belfast inland to Burnham Junction, where its single track connected with the MEC's Portland to Bangor mainline.

It continued to exchange passengers and mail with the MEC at their jointly owned station at Burnham Junction until 1960 and freight interchange traffic until 2002.In 1882, Maine Central leased the European and North American Railway (E&NA) between Bangor and Vanceboro.

This line was an important rail route for Canadian war material heading to the port of Saint John for shipment overseas to Europe.

In the months before the United States entered World War I, a German Army lieutenant attempted to blow up the railway bridge which crossed the St. Croix River at the international boundary.

Maine Central also operated a line southeast from Bangor along the coast through Machias to Calais, with branches to Bucksport, Bar Harbor and Eastport.

The Maine Central was at its height by 1917 when it became nationalized during World War I under the United States Railroad Administration, having trackage which extended over 1,358 miles (2,185 km).

It ran from Vanceboro, Calais and Eastport in the east, to Portland in the south, St. Johnsbury, Vermont in the west, and to Lime Ridge, Quebec in the north.

Faced with increased competition from cars, trucks and buses, Maine Central operated its last passenger train on September 5, 1960, and continued to reduce its freight business to reflect changing traffic.

One of the instigating factors which led to the labor strife at Guilford relates to a corporate reorganization at one of the company's former Maine Central properties.

Eventually, the corporate reorganization under Springfield Terminal would extend to the full extent of Guilford operations, and attempting to run a class 1 under short line rules would lead to years of union troubles.

Several railroad preservation and promotion groups are seeking to have the state-owned Calais Branch and Mountain Division routes reactivated for use by short line or tourist rail operations.

[10] Among the named trains operated by the MEC prior to ending passenger service in 1960 were the Bar Harbor Express, Down Easter, Flying Yankee, Gull, Katahdin, Kennebec, Mountaineer, Penobscot, Pine Tree, and Skipper.