The Heart River is a significant tributary of the Missouri River system, flowing approximately 180 miles through southwestern North Dakota from around Belfield to the Missouri River near Mandan. This prairie river drains an area of 3,370 square miles and passes through Stark, Grant, Morton, and Billings counties. The Heart River represents a diverse watershed that supports both game and non-game fish species, offering anglers opportunities for smallmouth bass, walleye, northern pike, and channel catfish fishing. From a biological perspective, the river maintains good overall health with diverse aquatic communities, though it faces challenges from agricultural runoff and sedimentation typical of prairie streams.