|Locale||Bristol County and Plymouth County, Massachusetts|
|Owner||CSX / MassDOT|
|Character||Elevated and Surface level|
|Track gauge||4 ft 8 1⁄2 in (1,435 mm)|
The line diverges from Amtrak's Northeast Corridor just north of Attleboro station. From there, it runs east through Norton then southeast through downtown Taunton. At Cotley Junction (near Weir Village), it separates from the New Bedford Subdivision and turns east. The line ends with a wye to the MBTA Commuter Rail Middleborough/Lakeville Line just south of downtown Middleborough.
The current Middleborough Subdivision is formed from sections of four different railroads built in the 19th century. The oldest section is from northwestern Taunton into downtown Taunton, opened in April 1836 as part of the Mansfield-Taunton Taunton Branch Railroad - one of the first railroad lines in New England. The New Bedford and Taunton Railroad completed an extension from Taunton south to New Bedford in 1840, including the current Middleboro Subdivision southeast of downtown Taunton. The Middleboro and Taunton Railroad opened a line from southeastern Taunton east to Middleborough in July 1856. In August 1871, the New Bedford and Taunton Railroad built a branch from Attleboro Junction in northwest Taunton to Attleboro.
The Old Colony acquired the Middleborough and Taunton Railroad in 1874. The same year, the New Bedford and Taunton Railroad became the New Bedford Railroad. It joined the Boston, Clinton, Fitchburg and New Bedford Railroad in 1876. The Old Colony acquired that system in 1879, and was itself merged into the New York, New Haven and Hartford Railroad in 1893. Regular passenger service ended in 1958, though summer-only trains from New York to Hyannis used the line from Attleboro to Middleborough from 1960 to 1964 and from Boston to Hyannis via Stoughton brefly in 1961.
The New Haven Railroad folded into Penn Central in 1969, and the line became part of Conrail in 1976. The Attleboro-Middleborough line was known as the Middleboro Secondary by the 1990s. The entire line was assigned to CSX in the 1999 breakup of Conrail, though CSX initially only applied the Middleboro Subdivision name west of Cotley Junction. From 1986 to 1996, the line was used by Amtrak's seasonal Cape Codder service.
The first phase of South Coast Rail is planned to use the Middleboro Subdivision to allow MBTA Commuter Rail service to reach the South Coast. As of March 2017[update], that service is projected to begin in 2022.
- "Albany Division Timetable No. 4" (PDF). CSX Transportation. November 1, 2004.
- Karr, Ronald Dale (1995). The Rail Lines of Southern New England. Branch Line Press. pp. 327–330. ISBN 0942147022.
- Belcher, Jonathan (March 25, 2017). "Changes to Transit Service in the MBTA district 1964-2017" (PDF). NETransit.
- "Conrail System Map Showing The Proposed Allocation Of Conrail Lines & Rights". Norfolk Southern Railroad. July 9, 1997 – via Mark D. Bej.
- Dungca, Nicole (March 22, 2017). "State changes gears on Middleborough commuter rail plan". Boston Globe. Retrieved April 10, 2017.