‘National Defense Area’ on the California-Mexico Border—What to Know

The designation revives a little-known Theodore Roosevelt-era directive that set aside federal lands for border protection more than a century ago.

A Texas National Guard soldier stands near the wall on the southern border during a sandstorm, as seen from Ciudad Juarez, Mexico, on March 6, 2025. Jose Luis Gonzalez/Reuters

Hundreds of acres of public land near the Mexico border have been put under the control of the U.S. Navy for the sake of national security.

The Trump administration announced the plan, which is a continuation of a project started by the Theodore Roosevelt administration, on Dec. 10. The land is now designated as a “National Defense Area.”