As a trading center, the city gradually began to lose its importance beginning from the early 20th century. The importance of Mengzi was ended by the construction of the French railway from Haiphong to Kunming (the Yunnan provincial capital) in 1906–10. This railway bypassed Mengzi, but in 1915 a branch line was built via the town to the Gejiu tin mines. Apart from a brief respite during the early days of World War II, the town of Mengzi has, nevertheless, steadily declined in importance ever since.