The Montreal, Maine & Atlantic Railway (AAR reporting mark: MMA) is a regional freight railroad operating in the U.S. states of Maine and Vermont and the Canadian provinces of New Brunswick and Quebec. Its Canadian subsidiary is Montreal, Maine & Atlantic Canada Company. The entire system is owned by RailWorld, Inc. and is headquartered near Bangor, ME.

Predecessor railroads

MMA was created in 2003 to operate several bankrupt railroads purchased by RailWorld, Inc. from holding company Iron Road Railways . These systems included:

• Bangor and Aroostook Railroad (BAR) which operated from Searsport, ME to Bangor, ME, Brownville Junction, ME and north to Aroostook County where it served Houlton, ME, Presque Isle, ME, Madawaska, ME, and Van Buren, ME.

• Canadian American Railroad (CADC) which operated the former Canadian Pacific Railway (CPR) Saint John, NB-Montreal, QC main line west of Brownville Junction to Lennoxville, QC

• Quebec Southern Railway (QSR) which operated the former CPR Saint John, NB-Montreal, QC main line west of Lennoxville, QC to Farnham, QC (later extended to St. Jean, QC and by trackage rights to Montreal, QC)

• Northern Vermont Railroad (NVR) which operated the former CPR Farnham, QC-Wells River, VT secondary main line.

• Van Buren Bridge Company (VBB) which operates a railway bridge crossing the St. John River, across the International Boundary, between BAR trackage in Van Buren, ME and Canadian National (CN) trackage in St. Leonard, NB

Interchange points

CN

• Saint John, NB (using NBSR/EMR)
• Sherbrooke, QC (using SLQ)
• St. Jean, QC
• St. Leonard, NB
• Ste. Rosalie, QC

CP

• St. Jean, QC

EMR/NBSR