It cuts through gently rolling hills of tallgrass, and its marshes teemed with waterfowl and other wildlife. It is the river the French trappers named the Marais des Cygnes (Marsh of the Swans). Melvern Lake, in the valley of that river, is still a haven for many of the wildlife species seen by the early trappers.

A good way to become familiar with the area is to walk on the Marais des Cygnes Nature Trail below the dam and on the Eisenhower Interpretive Trail in Eisenhower State Park. There are riparian woodlands of ash, American elm, cottonwood, and honey locust, and thickets of rough-leaved dogwood, smooth sumac, and wild plum. Hundreds of acres of big and little bluestem, Indiangrass, switchgrass, black sampson, black-eyed Susan, Illinois bundleflower, and dozens of other prairie plants are found here.

The river, lake, and cattail marshes provide habitat for many migrating waterfowl, shorebirds, and wading birds. In winter bald eagles perch in trees along the lake. Also watch for sharp-shinned, Cooper's, and rough-legged hawks. The waters attract snow geese, gadwalls, American wigeons, and common mergansers. Look in the woodlands and thickets for black-capped chickadees, red-breasted nuthatches, tufted titmice, and brown creepers. In spring, grasslands contain booming grounds, or leks, of greater prairie chickens. Summer birds include wood ducks, scissor-tailed flycatchers, eastern kingbirds, common nighthawks, and great blue herons. Year-round residents include red-tailed hawks, northern harriers, eastern screech-owls, Canada geese, belted kingfishers, and red-headed woodpeckers. Mammals such as white-tailed deer, squirrels, bobcats, coyotes, muskrats, and beaver can best be viewed just before sunup and just after sundown.