Final answer:
The Ozark and Ouachita Mountains are primarily found in Missouri, Arkansas, Oklahoma, and to a lesser extent, Kansas, with the Ouachitas being most prominent in Arkansas and eastern Oklahoma.
Step-by-step explanation:
The Ozark Mountains and Ouachita Mountains primarily span across several states, including Missouri, Arkansas, Oklahoma, and a small portion in Kansas. These regions are part of the U.S. Interior Highlands, which is the biggest mountainous region between the Appalachians and the Rocky Mountains. The Ouachita Mountains, however, are predominantly located within the state of Arkansas and extending into eastern Oklahoma.