The Missouri River Tributary is a river system that flows through the Midwest United States. Two of its major tributaries are the Osage and Platte Rivers. The Osage River is a 5-letter tributary that runs through Missouri, Kansas, and Oklahoma. It is a tributary of the Missouri River and is known for its scenic beauty. The Platte River is a 6-letter tributary that runs through Nebraska, Wyoming, and Colorado. It is also a tributary of the Missouri River and is known for its wide, shallow course.