Area code 858 serves the northern coastal and inland parts of San Diego County, California, including communities such as La Jolla, Del Mar, Mira Mesa, and Rancho Bernardo. It was created in 1999 as a split from area code 619 to accommodate the explosive growth of the San Diego region. The 858 area includes major tech and biotech hubs, especially around the University of California, San Diego, and the Torrey Pines research area. Known for its scenic coastline, affluent suburbs, and innovation-driven economy, 858 has become a key part of San Diego’s identity. It is home to many of the region’s most desirable residential and commercial communities. 858 continues to be a standalone code, although future growth may prompt additional numbering changes.