The Stony Brook Railroad (formally the Stony Brook Railroad Corporation), chartered in 1845, was a railroad company in Massachusetts, United States. The company constructed a rail line between the Nashua and Lowell Railroad's main line at the village of North Chelmsford and the town of Ayer, Massachusetts (then the village of South Groton) where it connected to the Fitchburg Railroad. Rather than running its own trains, upon opening in 1848 operations were contracted to the Nashua and Lowell; this arrangement continued until the Nashua and Lowell was leased by the Boston and Lowell Railroad in 1880. The Boston and Maine Railroad (B&M) took over operation of the Stony Brook in 1887 when it leased the Boston and Lowell Railroad. In 1983 the B&M was purchased by Guilford Rail System, which re