City of Rocks State Park, Volcanic rock formations in the Chihuahuan Desert, New Mexico, USA

City of Rocks State Park is a protected area of large, rounded tan and brown boulders in the Chihuahuan Desert of New Mexico. The bedrock is Kneeling Nun Tuff, a volcanic ash-flow tuff from the Emory Caldera eruption 34.9 million years ago. Erosion by freeze-thaw cycles and plant growth shaped pinnacles and boulders up to 40 feet (12 m) high, with narrow paths between them.

City of Rocks State Park was created by Chapter 110 of the 1953 Laws of New Mexico on March 20, 1953, which leased 640 acres from the Commissioner of Public Lands. The German source gives May 1952 as the founding date. The bedrock is the Kneeling Nun Tuff, laid down 34.9 million years ago by a VEI 8 eruption of the Emory Caldera.

The park features a desert botanical garden displaying regional plants including century plants, yucca, and multiple cactus species native to the area. Visitors can see how these plants thrive in the harsh landscape and adapt to extreme desert conditions.

The entrance lies about 29 miles from Deming and about 30 miles from Silver City, reached via U.S. Highway 180 at its junction with State Route 61 in Grant County. The park is open all year, with electric and water hookups, restrooms and hot showers for campers. The visitor center stands one mile south of the park entrance and sells maps, books, camping supplies and firewood. Three trails start here: Hydra (3.3 miles), Table Mountain (3 miles) and Cienega (about 2 miles).

The park's observatory offers monthly astronomy programs under dark skies where visitors can observe celestial objects through professional telescopes. These evening viewing sessions provide an opportunity to study the stars far from light pollution.