Also known as Anko, An was a member of the triad of the Sumerian High Gods (along with Enki and Enlil). He was the God of Heaven and the Universe, and was the primary God in the Sumerian pantheon from(approximately) 4000 B.C. to 2500 B.C., when his position was taken over by his sons Enlil and Enki.He also existed in Mesopotamian mythology as Anu According to Sumerian creation myths, when the earth was created An took the Heavens as his kingdom, whilst Enlil took the Earth as his.

According to many sources, he and Nihursag created almost all of the other gods of Sumaria, and along with Enlil, granted various gods, goddesses, and kings their earthly regions of influence and their laws. Erech was the centre of the cult of An worship, and the fall of An from being the highest of the Sumerian Gods coincides with the city losing its status as the most powerful in the region.