Complex sentence: Four years later, the Navajo signed a treaty that moved them onto a reservation in the Four Corners region that is today known as the Navajo Nation, the largest Native American reservation in the United States, encompassing with a population of over 180,000 as of 2000.
Split into simpler sentences: Four years later, the Navajo signed a treaty that moved them onto a reservation in the Four Corners region that is now known as the Navajo Nation. It is the largest Native American reservation in the United States, encompassing with a population of over 180,000 as of 2000.