At El Morro, the history of the Southwest is visible in the traces left by many generations of travelers. From about 1275 to 1400, Ancestral Puebloan people lived in villages on top of the sandstone rock, and some of their rooms remain visible today along with hundreds of petroglyphs carved into the rock face. From 1539 to 1774, Spanish expeditions entered what is now New Mexico, and inscriptions at El Morro include that of Governor Don Juan de Onate in 1605 and others dating to 1774. From 1846 to 1906, United States military expeditions and emigrants bound for California came through the area, and many of their names were carved on the rock. On December 8, 1906, President Theodore Roosevelt proclaimed El Morro a national monument under the Antiquities Act of 1906, helping preserve its inscriptions, petroglyphs, and pueblo ruins, and people still travel here today along routes followed for hundreds of years.