According to C. Michael Hogan, the associated Red River Fault was instrumental in forming the entire South China Sea at least as early as 37 million years before present.

The river is relatively shallow, and carries a lot of reddish silt along its way, appearing red brown in colour.

It flows generally southeastward, passing through Yi and Dai ethnic minority areas before leaving China through Yunnan's Honghe Autonomous Prefecture.

The late 19th-century French explorers were able to travel up the Red River until Manhao in South Yunnan, and then overland toward Kunming.

[5] The Red River remained the main commercial travel route between the French Indochina and Yunnan until the opening of the Kunming–Haiphong Railway in 1910.

[6] On the Manhao to Lao Cai section, where the current may be quite fast, especially during the freshet season, traveling upstream in an wupan was much more difficult than downstream.