Like the other coastal villages on Hudson and James Bay, Eastmain also started out as a Hudson's Bay Company trading post, originally called East Main House.
Eastmain is accessible by air (Eastmain River Airport) and by car over a gravel road linking it to the Route de la Baie James.
The Eastmain community was greatly affected by the James Bay Hydroelectric Project, which saw 90% of the Eastmain River diverted to the La Grande River in 1980.