The preserve was created by the State of Alaska in 1982.  It consists of 48,000 acres of river bottom land of the Chilkat, Kleheni, and Tsirku Rivers. During the months of October through December the bald eagle population is between 3,000 and 4,000. They arrive to feast on a late run of chum salmon.

A warm water upwelling at the confluence of the Chilkat and Tsirku Rivers contributes to the late salmon run.  There is a large amount of gravel and sand in the area which enables an underground reservoir of water that is generally 10-20 degrees warmer than the surrounding water.