A network of caves in rural Oregon may be the oldest site of human habitation in the Americas, suggesting that an ancient human population reached what is now the United States at the end of the last Ice Age, Oregon officials said on Friday.

That realization prompted the U.S. National Park service to add the Paisley Five Mile Point Caves to its list of nationally important archaeological and historical sites, the Oregon Parks and Recreation Department said in a statement.

Only recently have researchers become convinced that humans lived at the Paisley caves a thousand years before the human settlement that is documented in sites first discovered in the 1920s near Clovis, New Mexico, said Dennis Jenkins, director of the University of Oregon Archaeology Field School, in the statement.