Prior to the 1990s, the 150-mile international border that California shares with Mexico had seen nonstop illegal migration. In the 1990s, however, the U.S. Border Patrol began a concerted effort to establish and maintain control of the border, beginning in urban San Diego. This heightened law enforcement presence, known as Operation Gatekeeper, changed the westernmost portion of the border from the most permeable to the least permeable. This pushed illegal border crossers into more dangerous crossing areas in eastern San Diego and Imperial Counties, making their trip longer and the terrain and climate more dangerous. Death rates among illegal border crossers soared, impacting the resources and caseloads of forensic anthropologists in jurisdictions along the border. Bodies found in the new areas being used by border crossers decompose rapidly under the hot, dry climate, and there are minimal sources of antemortem data on the decedents. Many of these migrants are never identified. The traditional means of identifying unknown decedents are not successful. Cooperation between forensic scientists, investigative agencies, and Nations is necessary to prevent the rising number of unidentified deceased border crossers. 2 figures and 12 references