There are 15 US Post Offices in Imperial County serving a total of 188,847 residents equating to 12,590 residents per post office. It's estimated that approximately 301,421 packages are handled across the 15 county post offices annually. Imperial County is a county located in the U.S. state of California. As of the 2010 census, the population was 174,528. The county seat is El Centro. Established in 1907, it was the last county to be formed in California. Imperial County comprises the El Centro, CA Metropolitan Statistical Area. It is also part of the Southern California border region, the smallest but most economically diverse region in the state. It is located in the Imperial Valley, in the far southeast of California, bordering both Arizona and Mexico. Although this region is a desert, with high temperatures and low average rainfall of three inches (seventy-five mm) per year, the economy is heavily based on agriculture due to irrigation, supplied wholly from the Colorado River via the All-American Canal. The Imperial Valley is a melting pot of Anglo-American and Hispanic cultures. On the American side, the majority of residents are of Mexican American heritage, while the Mexican side was greatly influenced by American culture for many decades. The entire valley is a multi-racial mixture of whites, Asian Americans, some African Americans and Native Americans. In 2014, Imperial County had the second highest percentage of unemployed people of any county in the United States, at 23.6 percent."