Located on the 2,290-foot summit and flank of Pack Monadnock in Peterborough, Miller is the oldest state park in New Hampshire. A winding 1.3-mile paved road leading to the scenic summit is open for visitors to drive in summer and on spring and fall weekends. Picnicking and hiking are popular activities at the scenic mountain park. Three main hiking trails ascend Pack Monadnock to the summit. The best known is the Wapack Trail, which is a 21-mile footpath that extends from Mt. Watatic in Ashburnham, Massachusetts to North Pack Monadnock in Greenfield.

An operational fire tower, used for detecting fires, affords a panoramic view of the surrounding countryside. Mount Monadnock, 3,165 feet high, can be seen standing alone 12 miles to the west. It is believed Native Americans named the area's mountains, and that "pack" means little. Other peaks and hills of southern New Hampshire and adjacent Massachusetts can also be seen. On clear days views reach to Mount Washington, the skyscrapers of Boston, and the Vermont hills.

Miller is a carry-in/carry-out park; please carry your trash home with you and dispose of it properly.