The North China Plain is the flood plain of the Yellow River, and it holds the earliest Chinese religion that can be read rather than inferred.
At Anyang, the late Shang capital, tens of thousands of inscribed ox scapulae and turtle plastrons have been recovered. They were used for divination: a question was put, heat was applied to prepared hollows until the bone cracked, the crack was read, and in many cases the question, the reading and sometimes the outcome were then carved onto the bone. The subjects are the concerns of a royal house, harvests, rain, illness, childbirth, hunting, campaigns, and the correct sacrifices to particular ancestors on particular days.
What they show is a religion built around the royal ancestors and around a high power called Di, with a calendar of offerings so elaborate that the ancestral cult amounts to an administrative system. David Keightley's study of the corpus established how much of Chinese religious vocabulary and practice is already present there.
The Zhou conquest around 1045 BCE brought the idea that carried furthest. The mandate of heaven holds that heaven confers the right to rule on a virtuous house and withdraws it from an unworthy one, which explains both the conquest and any future conquest. It made political legitimacy a moral and religious question in a way that governed Chinese political thought for three thousand years, including the arguments of Confucius in the state of Lu on the same plain.