This is a concrete monument with a brass cap set by the Department of Agriculture Biological Survey in 1934 (now known as the U.S. Fish and Wildlife Service). We found the corner still standing but buried in a couple of feet of mud in the Mississippi River bottom just north of the City of Prairie du Chien. We replaced the corner with a 1″ by 60″ long iron stake. We drove it below the mud line so the corner couldn’t freeze into the ice and be pulled out when the water rose in the spring.