San Diego County is a county located on the Pacific Ocean in the far southwest of the U.S. state of California, United States along its border with Mexico. According to the 2000 Census, its population was 2,813,833, making it the third largest county by population in the state and the sixth largest in the country. The state of California estimates its population as of 2007 to be 3,098,269 people, increasing its rank to second place, ahead of Orange County. The county seat is the city of San Diego.