Part of the Pawtuckaway State Park system of trails, the Mountain Trail is a long, meandering piece of doubletrack that connects up to a few other trails in the system.
From the main parking area, you would run down Pawtuckaway Road for about 1/4 of a mile to get to the trail, which will be on your left side. There is limited parking at the trailhead.
As you turn onto Mountain Trail, glance to your right just past the gate and notice Woronoco Trail
coming in. Keep straight and follow the sign to stay on Mountain Trail. Quite a ways in, there will be another trail that comes in on the right; this is South Ridge Trail. Stay straight/left for Mountain Trail. Once you hit Tower Road, you know you've reached the end.