Modern Southwestern Mandarin was formed by the waves of immigrants brought to the regions during the Ming and Qing Dynasties. Because of the comparatively recent move, such dialects show more similarity to modern Standard Mandarin than to other varieties of Chinese like Cantonese or Hokkien. For example, like most Southern Chinese dialects, Southwestern Mandarin does not possess the retroflex consonants (zh, ch, sh, r) of Standard Mandarin, but most varieties of it also fail to retain the checked tone that all southern dialects have.
The Chengdu-Chongqing and Hubei dialects are believed to reflect aspects of the Mandarin lingua franca that was spoken during the Ming. However, some scholars believe its origins may be more similar to Lower Yangtze Mandarin. Though part of the Mandarin group, Southwestern Mandarin has many striking and pronounced differences with Standard Mandarin such that until 1955, it was generally categorized alongside Cantonese and Wu Chinese as a branch of Chinese varieties.