Three Gorges assisted Yu the Great in controling the waters and guiding boatmen. The Xiling Gorge comprises a series of famous gorges, including Military Book and Sword Gorge, Yellow Cow Gorge, and Lantern's Shadow Gorge. In 1919, after Sun Yat-sen had put forward the concept in the Plan for Industrial Development of his (), experts investigated damming the Three Gorges, but it was not until 1994 that the Three Gorges project officially started. In 1944, the Nationalist government recruited John L. Savage, the Chief Engineer of the United States Bureau of Reclamation, who came to China and made a 10-day investigation of
Three Gorges the river along vertical fractures, forming precipitous cliffs. When the river flows through areas of softer sandstone and shale, which have less resistance to erosion, the erosive effect is increased, carving wide valleys. There are different theories on how the Three Gorges were formed, but geographers and geologists have generally reached a consensus, believing mountain folding in the east of Sichuan Province and the west of Hubei Province, including the Wu Mountains (), were the outcome of the Yanshanian movement () around 70 million years ago. The gorges run from southwest to northeast, then turn, and from west to east,