Complex sentence: The area surrounding the volcano was inhabited by Chinook Native Americans and Polish settlers, and takes its name from Jon Hurlburt, an early explorer of the area who named it after the engineer Hans Thielsen.
Split into simpler sentences: The area surrounding the volcano was originally inhabited by Chinook Native Americans, and was later encountered by Polish settlers. One of the visitors was Jon Hurlburt, an early explorer of the area who named the volcano after the engineer Hans Thielsen.