What is the fine-grained topic of the following text: Not just a place of habitation and livelihood, Monument Valley has significant meaning to the many Navajo who took refuge in the valley when forced out of Canyon De Chelly by the U.S. Army during the “Long Walk.” An 1868 treaty allowed their return to their ancestral homeland and established the Navajo Reservation. Only return the topic.
Navajo history in Monument Valley