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.
Zichang City, which is directly under the jurisdiction of Shaanxi Province and managed by Yan'an City, is located in the middle of the Loess Plateau, Hengshan District to the north, Zizhou County and Qingjian County to the east, Yanchuan County and Yanan County to the south, Ansai District and Jingbian County to the west, between longitude 109o1158 "- 110o0120022" east and latitude 36 °593030 "- 37 °300000N, with a total area of 2405 square kilometers. The county seat is 93 kilometers away from Yan'an and 430 kilometers away from the provincial capital Xi'an. In 31 (1942), in memory of the national hero Xie Zichang, he changed his name to Zichang County, the hometown of Xie Zichang, the foothold of the long March of the Central Red Army and the starting place of the Anti-Japanese Eastern Expedition. The late agrarian revolution was the seat of the CPC Central Committee and the Chinese Soviet government, and after the founding of the people's Republic of China.