Why was travel into and out of Sichuan difficult for centuries?

For centuries, travel into and out of Sichuan was extremely difficult due to the province's rugged, mountainous geography, which effectively isolated the region. The Sichuan Basin is surrounded on all sides by lofty highlands and mountain ranges that created significant natural barriers.1234

The primary historical routes were treacherous and limited:2
* East: Travel required navigating the dangerous Yangtze Gorges, which served as a major, albeit hazardous, entrance.2
* North: Access was restricted to a difficult, treacherous plank road that crossed the mountains.2
* West: Movement was hindered by deep canyons and the swift, powerful currents of the Dadu and Jinsha rivers.2

These geographic challenges made the construction and maintenance of transportation infrastructure costly and hazardous, often involving steep slopes, hairpin turns, and the constant threat of landslides. It was not until the 1950s that significant efforts, such as the construction of railways across the mountains and steel bridges over western rivers, began to substantially improve connectivity to the rest of China.2