The 1990s bore witness to significant advances in the study of Chinese migration history. This paper explores ways in which these new insights into population and migration patterns in the lower Yangtze watershed throw light on the history of dialects currently assigned to the Jiāng-Huái family by the Language atlas of China. It is found that the lexical corpora of many of these dialects were laid down as the result of two migration waves, one during the late Táng period and the other after the fall of the Northern Sòng. Material from the first of these waves is now found in bái or colloquial pronunciations of certain syllables. Material from the second wave constitutes the primary lexical component of these dialects and also contributes those wén or literary readings which pair directly with the colloquial pronunciations in each dialect. Interaction with several contiguous dialect groups is also noted. In particular, interlocking or commensurate wén/bái correspondences with dialects of the Northern Wú group are discussed and exemplified.