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.
Dongguan, one of the prefecture-level cities under the jurisdiction of Guangdong Province, one of the central cities of the Pearl River Delta and one of the cities of Guangdong-Hong Kong-Macau Greater Bay Area, is a central city on the east coast of the Pearl River Delta approved by the State Council. By 2018, the city had jurisdiction over 4 streets and 28 towns, with a land area of 2460.1 square kilometers, a sea area of 82.57 square kilometers, a resident population of 8.3922 million, and an urban population of 7.6386 million, with an urbanization rate of 91.02%. Dongguan is located in the central and southern part of Guangdong Province, the east bank of the Pearl River Estuary, Guangzhou in the northwest, Shenzhen in the south and Huizhou in the northeast. Dongguan is the first of the "four little tigers of Guangdong" and is known as the "factory of the world". It is also one of the five prefecture-level cities without districts and one of the new first-tier cities in the country. Dongguan established a county during the period of the three Kingdoms.