Following the fall of an earlier dynasty, the dynasty reunified china in 960 ce.

The Song dinasty began in 960 and lasted until 1278. It succeded Five Dynasty Period. Song Dynasty was the first in the world to issue banknotes ( printed paper money ). During the Song dynasty China had sustainable growth in population and economy. Following the fall of earlier dynasty, the Song dynasty reunified China in 960 CE.

In the midwest because it has more moderate climate than the north or south west which makes farming far easier.