Sanmenxia's history begins with the Yangshao culture (5000-3000 BC), first discovered at Yangshao Village in Mianchi County in 1921. This archaeological breakthrough established the existence of a sophisticated Neolithic civilization in the Yellow River valley.
During the Western Zhou Dynasty, the area was home to the State of Guo, a significant vassal kingdom. The State of Guo Cemetery, discovered in the 1990s, yielded thousands of exquisite bronze, jade, and iron artifacts.
Hangu Pass became critically important during the Warring States period (475-221 BC) as the defensive gateway for the Qin State. The pass's strategic significance continued through the Han, Tang, and subsequent dynasties. The Taoist classic Tao Te Ching is said to have been written here.
The modern era brought the ambitious Sanmenxia Dam project (1957-1960), China's first large-scale hydroelectric project on the Yellow River. The dam and its associated infrastructure transformed the region's economy and landscape.
Sanmenxia was established as a prefecture-level city in 1986, encompassing the historical and cultural treasures of this ancient crossroads region.