San Diego (/ˌsæn diˈeɪɡoʊ/ SAN dee-AY-goh, Spanish: [san ˈdjeɣo]; Spanish for 'Saint Didacus') is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States and the seat of San Diego County, the fifth most populous county in the United States, with 3,338,330 estimated residents as of 2019. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center. San Diego is the second largest city in the state of California, after Los Angeles.
Ansai District, which belongs to Yan'an City, Shaanxi Province, is located in the hinterland of the inland Loess Plateau, the edge of Ordos Basin, in the north of Shaanxi Province, due north of Yan'an City, west of Zhidan County, Jingbian County of Yulin City in the north, Zichang County in the east, and Ganquan County and Baota District in the south. Between longitude 108 °5 "44"-109 °26 "18" east and latitude 36 °30 °45 "- 37 °19" 3 "north. The distance between the north and south lines is 92 kilometers, and the east-west distance is 36 kilometers, with a total area of 2950 square kilometers, accounting for 8.04 percent of the total area of Yan'an. Ansai has been known as the "upper county throat" since ancient times. It is located in the cultural fusion zone in which the national culture of the Central Plains represented by Yangshao culture develops northward and the northern national culture represented by Yinshan rock painting culture develops to the south.