This line was to serve the New Hampshire towns on the eastern side of Mount Monadnock, mainly Jaffrey and Peterborough.
The Boston, Barre and Gardner Railroad, running south from Winchendon, leased the Monadnock in 1874 in order to have a line to Concord.
In 1880, the BB&GRR fell on hard times and transferred the lease to the Cheshire Railroad in order to keep it out of the hands of the Boston and Albany Railroad which had taken over the Ware River in 1873 and wanted to have access to the Monadnock Region.
The Monadnock became part of the Fitchburg, along with the entire Cheshire, in 1890 and then to the Boston and Maine Railroad in 1900.
Through service ended on the line after the floods caused by the 1938 Hurricane, but local passenger trains continued to run until 1953.