On older maps, the Alsek river is labeled as the Kaskawulsh and The Tatshenshini as the Alsek. Some Yukon First Nation elders also refer to the river as the Kaskawulsh.
The river flows next to the Lowell glacier which has sometimes blocked off the river and created a large lake behind it, "Neoglacial Lake Alsek." The last such blockage took place in 1850; its release created a massive flood, washing away everything in its path on the way to the Pacific.
The river carries a lot of silt from the Alsek lake/glacier, which contributes to the river's low temperature.
The Alsek and nearby East Alsek rivers were at one time connected, and the old river bed can still be made out on some maps.
The Alsek glacier contacts the Grand Plateau glacier, which faces the shoreline. Also in the same general area are the Doame foothills and Doame River.
Alsek River (in distance) near junction with Sugden Creek inside Kluane National Park
The first known kayak descent of Turnback Canyon was by Walt Blackadar, who ran the canyon solo on August 25, 1971. He wrote about his trip for Sports Illustrated. "This has been a day!," he wrote in his journal. "I want any other kayaker or would-be expert to read my words well. The Alsek Gorge is unpaddleable!" Despite this sincere warning from a man who apparently felt lucky to be alive, groups of expert kayakers have successfully run Turnback Canyon since then. A prominent mountain which overlooks the Alsek was named Mount Blackadar in his honor.
The Alsek and East Alsek rivers are a part of the Yakutat area limited entry set gillnet fishery. Both rivers produce king, silver, and sockeye commercially. Chum and pink salmon can also be caught, but are not generally sought after due to their relative lack of worth/quality. These two rivers can be characterized as low volume fisheries, while the Alsek river in particular produces particularly high quality salmon due to its low temperature. The Alsek's silt content also prevents the sun from damaging the fish.
The area also supports subsistence and sport fishing. There are multiple local sport fishing, sight-seeing, hunting, and animal watching lodges