To what area does 江南 refer? 早期的江南地区主要是古越族人的居住地，他们使用的古越语与古汉语相差很远。后来，北方汉人几次大规模的南迁使得北方古汉语被带到了江南各地，于是逐步形成了现在的各个方言。
My geography is not good.
Is 江南 everything south of 长江, or just the Southeast corner of China?
Wikipedia describes Jiangnan as:

Jiangnan or Jiang Nan (Chinese: 江南; pinyin: Jiāngnán; formerly romanized Kiang-nan, literally &quot;South of the River&quot; meaning &quot;South of the Yangtze&quot;) is a geographic area in China referring to lands immediately to the south of the lower reaches of the Yangtze River, including the southern part of its delta. The region encompasses the city of Shanghai, the southern part of Jiangsu Province, the southeastern part of Anhui Province, the northern part of Jiangxi Province and the northern part of Zhejiang Province. The most important cities in the area include Anqing, Changzhou, Hangzhou, Nanjing, Ningbo, Shaoxing, Suzhou, Wuxi, Wenzhou, and Zhenjiang.