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.
Haidong is a prefecture-level city under the jurisdiction of Qinghai Province, named because it is located to the east of Qinghai Lake; it belongs to the mosaic zone from the Loess Plateau to the Qinghai-Tibet Plateau, with a semi-arid continental climate; the city has a total area of 13200 square kilometers and has jurisdiction over 2 districts and 4 autonomous counties; in 2017, it has a resident population of 1.4708 million. Haidong has a long history. In the long historical evolution, Hehuang region has changed from the primitive nomadic state of "living after water and grass" to a more developed farming civilization. The people of all ethnic groups in Hehuang have jointly developed and built this land, creating a splendid history and culture. In December 2016, it was listed as the third batch of national comprehensive pilot areas for new urbanization. In 2017, the GDP of Haidong City was 43.6 billion yuan, an increase of 8.4 percent over the previous year at comparable prices. Among them, the added value of the primary industry