The name is an anglicization of Reka Kasilova, the name given to the river by early Russian settlers in the area.

[1] It begins at Tustumena Lake and flows northwest to Cook Inlet near Kasilof.

The upper section of the river is very swift, with several sections considered Class II whitewater, and underwater hazards are difficult to detect, due to the silty nature of the glacial runoff that comprises most of the river.

At mile 109 of the Sterling Highway, adjacent to the bridge where the highway crosses the river is the Kasilof River State Recreation Site, a day-use only park with picnic areas and a boat launch.

[3] The Crooked Creek State Recreation Site has a large campground and walk-in access to the point where Crooked Creek joins the river, a prime salmon fishing spot.