Clay Prairie is a 3-acre preserve containing a small, unplowed portion of the historic Butler Center Cemetery. It is located fifteen miles north of Parkersburg in central Butler County. In 1961, Joseph B. Clay gave the prairie to the University of Northern Iowa Foundation to be used for research and public education. The prairie is now one of the University of Northern Iowa’s biological preserves and was officially dedicated in 1976 as a biological state preserve.

The gently sloping terrain of the preserve is typical of that found in the Iowan Surface landform region. Ninety-eight plant species can be found here, with spring flora displays starting with thousands of shooting stars. Junegrass and porcupine grass, early prairie grasses, can be found among prairie smoke and heart-leaved golden alexanders. As summer approaches, the flowering of New Jersey tea, Indian paintbrush, gray-headed coneflower, and rattlesnake master begins. In fall, the blooms of Canada goldenrod, asters, and downy gentian are mixed with big bluestem, little bluestem, Indian grass, and prairie cordgrass.