Mossy Glen is an 80-acre preserve featuring a rugged forested area along the Silurian Escarpment. It is located 6 miles northwest of Edgewood and 6.5 miles northeast of Strawberry Point in Clayton County. The area was donated to the Iowa Conservation Commission in 1978 by Mildred Hatch in memory of her father, Charles A. Hesner, and her uncle, Henry Hesner. The area was dedicated in 1979 as a biological and geological state preserve.

The preserve is representative of a prominent line of bluffs across northeastern Iowa known as the Silurian Escarpment. This escarpment consists of massive outcrops of 430-millon-year-old dolomite (magnesium-rich limestone) formed in a shallow sea during what geologists term the Silurian period. The Silurian Escarpment forms the southwestern boundary of the Paleozoic Plateau landform region, a broad area of rugged topography in northeast Iowa. Extensive rock outcrops, slumped dolomite blocks, steeply dissected ravines, and “karst” terrain (including sinkholes, springs, and caves) are characteristic of the rugged landscape found along the Silurian Escarpment. Mossy Glen contains several of these distinctive features.