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.
Yanchang County, which belongs to Yan'an City, Shaanxi Province, is located in the north of Shaanxi Province and east of Yan'an City. It is 73 kilometers from east to west and 55 kilometers from north to south, with a total area of 2368.7 square kilometers. The early human activities in Yanchang County can be traced back to the Neolithic Age. Western Jin Tai began two years (266 years), established the establishment of the county. Several changes, to the second year of Tang Guangde (764), because the Yanhe River from the county from west to east into the Yellow River, the name Yanchang County, still in use. The terrain tilts from northwest to southeast, high in the north and south, low in the middle, showing a valley peak type. Is a warm temperate dry continental monsoon climate, spring, summer, autumn and winter four distinct seasons, cold, warm, dry and wet. By 2018, Yanchang County had jurisdiction over one street and seven towns with a resident population of 128500, achieving a GDP of 54.077.