The county seat is in Wenlan town.
The Mengzi region is well-known for a dish called ''guoqiao mixian'' , made with long rice-flour noodles.
In the 19th century, Mengzi was a trading centre for commerce between the interior of Yunnan and the Hanoi-Haiphong area of Vietnam.
In 1886, a convention chose Mengzi to be the center of trade in Yunnan province for importing and exporting goods via Tongking in Vietnam. Facilities for this opened 2 years later.
Communications were inconvenient: goods were shipped to Hekou on the Vietnamese border by junk, transferred by small craft to Manhao, and then taken 60 km by pack animal to Mengzi. Despite these difficulties, Mengzi was an important port of entry into both Yunnan and western Guizhou provinces, and in 1889 it was opened to foreign trade as a treaty port. Most of this foreign trade was in tin and opium. Its main exports were tin and opium, and the main imports were mostly textiles and tobacco.
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 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.
Gejiu became a county in 1913, and a city in 1951. With the improvement of communications and transportation between cities of Gejiu and Kaiyuan and the other counties nearby, plus the development of trade between southwestern China and the countries of Southeast Asia, Mengzi's ties have increasingly strengthened with Gejiu and Kaiyuan. The whole area has become a border economic centre. In addition to tin, the county's natural resources include coal, manganese, lead, zinc, and antimony.
When Japanese troops drove Beijing and Tianjin university professors, students, and administrators out of those cities, and then later out of Changsha as well, the academics made their own long march to Yunnan Province. They first established themselves in Mengzi, but after a year or so moved on to the provincial capital, Kunming. This was Lianda, or the Southwest Associated Universities.
Recently, the prefectural government has moved from nearby Gejiu to Mengzi. New wealthy suburbs and large government offices have sprung up as a result, but much of the poverty remains, creating a large wealth gap within the city.
Like nearby Gejiu, mining, mostly of tin, is a large part of its economy.