Ganges is perhaps the holiest river of not just India but of world in terms of most number of people who treat a river a Holy.
It starts from Gangotri in Uttarakhand and flows from state of Uttar Pradesh, Bihar and West Bengal before entering in Bangla Desh where it meets Brahma Putra and makes the largest delta of the world.
So to answer your question - States are total four i.e. Uttarakhand, Uttar Pradesh, Bihar and West Bengal.
