More than worth its salt

Further evidence comes from the Qin Dynasty (221-206 BC) bamboo slips unearthed in the Liye ancient city in Hunan province. The inscriptions record Yushan salt being sold as far away as present-day Liye, confirming its wide commercial reach.

"The focus of salt archaeology has often been on production rather than circulation and trade," Wang says.

"This is the first time we've traced the actual circulation of Yushan salt. It marks a major breakthrough in understanding how well salt contributed to regional civilization."

Chongqing is the birthplace of China's salt archaeology. Since the 1990s, excavations across the Three Gorges region have established a systematic research framework for studying ancient salt production.

"Over the past two decades, Chongqing has reconstructed an evolutionary sequence of well salt-making techniques spanning nearly 4,600 years, from the Neolithic era to modern times," says Niu.

"The salt industry encouraged specialized craftsmanship, division of labor and, ultimately, greater social complexity."

The nearby Zhongba site, for example, has produced evidence of industrial-scale salt production before the Qin Dynasty. In just one square meter of excavation, archaeologists recovered around 130,000 pottery fragments, a staggering figure pointing to massive output and a highly specialized workforce. The industry also drove related sectors, including pottery-making, fuel supply and transportation.

"Such a highly specialized production system is a key indicator of social complexity," Niu says.

Salt production also played a decisive role in regional civilization, he adds. Wealth generated from salt helped establish the Ba state, which occupied parts of present-day Sichuan province and Chongqing during the Zhou Dynasty (c.11th century-256 BC).

Salt later became a strategic resource fought over by rival states. Ba and Chu repeatedly clashed over salt-producing regions, and after Qin conquered Ba, Qin and Chu continued competing for control of these valuable resources for more than four decades, highlighting salt's importance in ancient geopolitics.

"Our work at Zhongbao confirms that Yushan was producing salt before the Qin Dynasty and held strategic importance," Niu says.

"The site provides crucial archaeological evidence for understanding how salt drove social development and shaped regional civilization."