Zigong (, ), formed by the merger of the two former towns of Ziliujing (Tzuliuching, literally "self-flow well") and Gongjing (Kungching, literally "offering well"), is a prefecture-level city in Sichuan, southwestern China. Demographics According to the 2020 Chinese census, the prefecture-level city of Zigong has a population of 2,489,256 inhabitants, less than its population in 2010 (the average annual population growth for the period 2010–2020 was of -0.73%). However, the built-up (or metro) area, consisting of the 4 urban districts, grew, with 1,297,695 inhabitants (1,262,064 in 2010). History The area of Zigong has a long history in ancient China - with the invention and development of "Percussion Drilling rig" being one of the city's accomplishments. There are essentially two cities - that of the old and the new. The city was reached by rail in the 1950s. Several four-lane highways reach the city from other cities in the Sichuan province. The new city of Zigong has been modernizing since the late 1970s - but more rapidly since the early 1990s. The old "Salt" city is based on industry and farmland and a new "Tourism" city which caters primarily to Chinese tourists (as Zigong is better known within mainland China). Zigong is host to the Sichuan University of Science and Engineering as well as a new High Technology Zone. Economy Salt was once one of the major sources of revenue for China. To give an idea of how much money was generated from salt in China - after the fall of the last emperor, the Republic of China under Sun Yat-sen secured loans based upon the revenues of the Chinese Salt Administration (the government agency in charge of taxation on salt). The chief inspector of that administration stated "The best salt in China is produced from the salt wells of Sichuan". The best salt wells in Sichuan are in Ziliujing District, Zigong. The people of Zigong have been drilling in the area for Salt since before the Han Dynasty (76-88 A.D.) to extract salt from brine. Some historian estimates are that China has been active in producing salt since about 6000 BC. The brine aquifers in the area have salinity of at least 50 grams per liter. The classical method of drilling and production was the following: a drilling rig is erected and a borehole is drilled using a drilling bit and rope. Brine is extracted by dropping a long tube