Cedar Hills Sand Prairie is a 36-acre preserve containing a sand prairie, sedge meadow, and small fen. It is located ten miles northwest of Cedar Falls in western Black Hawk County. Formerly known as “Mark Sand Prairie,” it has been managed by the University of Northern Iowa Biological Preserves since its discovery in 1969. It was acquired by the Iowa chapter of The Nature Conservancy in 1985 from Wayne Mark. The preserve was dedicated in 1985 for its biological and geological features. Located in the Iowan Surface landform region, the preserve sits atop a broad sandy divide between the Cedar River and Beaver Creek, and is one of a series of aeolian (wind-formed) sandy ridges found along the Cedar River valley. Within the preserve, dry sand prairie occupies the upland ridges and sedge meadow occupies a large swale in the northeastern portion of the preserve. A small fen is found on seepy, peaty soil in a portion of the sedge meadow. Small marshes are found in the southwest corner of the preserve. More than 360 native species of grasses and forbs have been identified here, plus at least 107 species of diatoms. Little bluestem, porcupine grass, big bluestem, Indian grass, and prairie cordgrass are common grasses found along a dry to wet gradient. In the spring, marsh marigold is very showy in the swales, followed by hoary and hairy puccoons on the sandy slopes, bird’s-foot violet and thimbleweed on the upland prairies, and blue flag iris and shooting star on the moist lowlands. Prairie larkspur, wild rose, and black-eyed Susan bloom in the summer months. In late summer, the purple flowers of rough and prairie blazing stars can be spectacular. Asters and bottle gentian are among the last flowers to bloom in the fall. Over fifty species of birds can be found here, including bobolink, yellowheaded blackbird, upland sandpiper, grasshopper sparrow, and savannah sparrow. Plains pocket gophers, masked shrews, short-tailed shrews, and western harvest mice are common in the dry sand prairie, while whitefooted mice, deer mice, and meadow voles are common in the moist swale and transitional zones of the preserve. Over fifty species of butterflies have been found at the preserve as well, including the regal fritillary, Arogos skipper, Iowa skipper, gorgone checkerspot, two-spotted skipper, black dash, dion skipper, and broad-winged skipper. In August, migrating monarch butterflies gather by the thousands before they continue their journey south. Hunting is not permitted. Other natural areas in the vicinity include Clay Prairie State Preserve, Hartman Bluff State Preserve, and George Wyth State Park.