NOTE: This trail is no longer legally doable & we will not record any further FKTs. We keep the route for the sake of completeness. Do the New England Trail instead.
The Metacomet-Monadnock Trail (M&M Trail) is a 114-mile (183 km) hiking trail that traverses the Metacomet Ridge of the Pioneer Valley region of Massachusetts and the central uplands of Massachusetts and southern New Hampshire.
Here are some links for more info:
Lee-Stuart Evans updated the situation with this trail (Nov 2020): "Jimmy Mac and I went out again on the 'metacomet monadnock' trail and it's definitely dead. It shares 80% with the New England Trail and causes some confusion. The sections that aren't shared are impassable, or no longer legal to cross. The New England Trail guys have emailed me to explain that the MM sections that don't share the NET are being abandoned."