The Middleboro Subdivision is a railroad line owned by CSX Transportation in the U.S. state of Massachusetts. The line runs from Attleboro southeast to the beginning of the New Bedford Subdivision near Weir Village (in Taunton) along a former New York, New Haven and Hartford Railroad line. Its north end is at Amtrak's Northeast Corridor, over which CSX has trackage rights to reach the Framingham Subdivision at Mansfield and the Boston Subdivision in Boston (via the Dorchester Branch).
The oldest section of the Middleboro Subdivision is from northwestern Taunton into downtown Taunton, opened in 1836 as part of the Mansfield-Taunton Taunton Branch Railroad. 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, and the Old Colony Railroad built a branch from northwestern Taunton west to Attleboro around 1870. The lines became part of the NYNH&H and Conrail through leases, mergers, and takeovers, and 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, but CSX only applied the Middleboro Subdivision name west of the junction with the New Bedford Subdivision.
- CSX Timetables: Middleboro Subdivision
- Hon. Edward Appleton, Railway Commissioner, History of the Railways of Massachusetts, 1871
- Conrail System Map Showing The Proposed Allocation Of Conrail Lines & Rights, July 9, 1997