The route begins at I-5 near the Mexican border in a far south part of San Ysidro, a neighborhood of San Diego. As it starts its journey northward, it quickly has a junction with State Route 905 (SR 905) before exiting the city of San Diego and entering Chula Vista. Within the past 20 years the freeway has delineated the apparent divide between rich and poor in the city of Chula Vista; those on the eastern side of the freeway have been more affluent and have better schools compared to those on the western side. Just outside the city, I-805 meets County Route S17 (CR S17), also named Bonita Road, before coming to an interchange with SR 54. The freeway then enters National City, where it intersects Sweetwater Road and Plaza Boulevard, before leaving the city and reentering the city of San Diego.