[10] Snyder-Middleswarth Natural Area is in Spring Township in western Snyder County, about 5 miles (8 km) west of Troxelville on Swift Run Road.

The land that became Snyder-Middleswarth Natural Area was purchased by the state in 1902, as part of a larger 14,000 acre (56.66 km) parcel.

By 1923 the park had a telephone and some structures, and in 1937 the state named it a "Forest Monument" as an "area of botanical or historic interest".

[15] Snyder-Middleswarth was still a "State Forest Park" on the official 1965 Pennsylvania Department of Highways Snyder County map.

[16] In November 1967, the park was named a National Natural Landmark, as an "outstanding example of a relict forest composed predominantly of hemlock, birch, and pine, with scattered oaks".

Snyder-Middleswarth's virgin forest is thought to have survived at least in part due to its location and the difficulty of transporting the cut timber,[1] although the fact that many of the trees were brittle hemlock may also have preserved them.

[5] However, Thwaites (1992) wrote that the park was only the 8 acre (3.2 ha) picnic area, but distinguished it from the "much larger Snyder Middleswarth National Natural Landmark" (without giving its exact size).