Complex sentence: Latah County is the only county in the U.S. established by an act of Congress; it was originally part of Nez Perce County, which was reluctant to lose its most populated area.
Split into simpler sentences: Latah County is the only county in the U.S. established by an act of Congress. It was originally part of Nez Perce County, which did not want to lose its most populated area.