Areas of Critical Environmental Concern (ACEC) is a conservation ecology program in the Western United States, managed by the Bureau of Land Management (BLM). The ACEC program was conceived in the 1976 Federal Lands Policy and Management Act (FLPMA), which established the first conservation ecology mandate for the BLM. The FLPMA mandate directs the BLM to protect important riparian corridors, threatened and endangered species habitats, cultural and archeological resources, as well as unique scenic landscapes that the agency assesses as in need of special management attention.

The Big Maria Mountains are located in the southeastern part of the U.S. state of California, near the Colorado River and Arizona. The range lies between Blythe and Vidal, and west of U.S. Route 95 in California and east of Midland. The mountains are home to the Eagle Nest Mine and reach an elevation of 1,030 m (3,380 ft). A power line that runs from Parker Dam to Yuma, Arizona runs through the range. A smaller range, the Little Maria Mountains, lie to the west of the Big Marias.