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.
Gaotai County, which belongs to Zhangye City, Gansu Province, is located in the middle of Hexi Corridor and the lower reaches of Heihe River. it has been known as "Hexi key, five counties throat" since ancient times. The terrain is high in the north and south and low in the middle, with the northern foot of the Qilian Mountains in the south, the Heli Mountain in the north, the oasis plain in the middle, and the Heihe River running through the county. The county has a total land area of 4346.61 square kilometers and has jurisdiction over 9 towns. By the end of 2017, Gaotai County had a total population of 158000. Gaotai County has a long history, Han Wudi Yuanding six years (111 years ago) set the table as a county, when the "Silk Road" must pass. In the first year of Xiankang in the Eastern Jin Dynasty (335 BC), Zhang Jun of Qianliang set up Jiankang County in Camel City. Qing Yongzheng three years (1725), and Gaotai, town Yi Shou Qianhu Gaotai County. There are ancient ruins of Camel City and Xu Sanwan City in the territory.