Petersham to Ashburnham
101 was the number formerly used for what is now US 44. That 101 was decommissioned in 1935 when 44 was posted.
It didn’t stay retired for long, however, as it was posted along its modern route from to Ashburnham and up to at least MA 119 between 1939 and 1942. By 1954, 101 was extended west to Petersham.