This source is an online newspaper called The Indian Reporter. Beginning on page 4, the report discusses the "Humboldt Volunteer" program and the "Trinity Rangers" and the effects these groups had on the Whilkut tribe.
This map shows the specific region of Northern California in which the Whilkut people lived. This map displays the territory in detail and also includes the surrounding territories of other native tribes that also spoke Athabascan languages.