In northeastern Clay Co. Four miles north on N-18 from U.S. 18, Smith's Slough is on the west side. An access road going west off N-18, just north of Mud Lake to the east, skirts the north and west sides of the slough.

One of Iowa's most historic prairie pothole wetland areas, Dewey's Pasture WMA is a National Natural Landmark. Its abundant marshes, shallow lakes and extensive grasslands offer significant nesting, feeding and migration staging habitatfor waterfowl, shorebirds and others. Cryptic marshbirds nest on the marhes, and uplands offer nesting habitat for a number of declining neotropical migrants. It also is a candidate for future DNR designation as a nationally significant Bird Conservation Area.

From US Highway 18 between Spncer and Emmetsburg, turn north on County Highway N18 approximately 1/2 mile west of Ruthven. N18 passes Barriger Slough, Lost Island Lake and bisects the center of the Dewey's Pasture-Smith's Slough-Trumbell Lake wetlands complex. There are numerours parking areas, turn-offs and other places for easy observation of birds.