The part from Fitchburg south to Pratt Junction (in Sterling) opened in 1850 as part of the Fitchburg and Worcester Railroad.[4]: 238 At the other end, the Boston and Worcester Railroad opened a branch from Framingham northwest to Framingham Center in 1849.[4]: 348 The Agricultural Branch Railroad opened in 1855 from Framingham Center west to Northborough and in 1866 to Pratts Junction.[5] The entire line became part of the NYNH&H and Conrail through leases, mergers, and takeovers, and was assigned to CSX in the 1999 breakup of Conrail.