RIO GRANDE DEL NORTE, NM—Samuel Gomez, the war chief for Taos Pueblo, was in Washington, D.C., on March 25, as U.S. President Barack Obama proclaimed a new national monument near the tribe’s reservation in northern New Mexico.

The Río Grande del Norte National Monument covers more than 240,000 acres of federal land. The site includes historic Pueblo sites and petroglyphs that date back thousands of years.

“This extraordinary landscape of extreme beauty and daunting harshness is known as the Río Grande del Norte, and its extraordinary array of scientific and historic resources offer...