Townsend's chipmunk is the largest member of the genus in Oregon.The pelage of this chipmunk is dark and dull but as in other Oregon chipmunks, there is a dark brown to blackish middorsal stripe with alternate light and dark stripes, laterally, a total of five dark and four light stripes. Alternate dark (three) and light (two) stripes adorn the sides of the face. The throat, belly, and a patch behind the ear are white. The tail is black on the tip and the margins are frosted above with buff or white-tipped hairs.
Townsend's chipmunks have been found on the west slope of the Cascade Range in Clackamas, Linn, and Lane counties in old-growth forests and clear-cuttings. They tend to be more secretive than most and are heard more often than seen. When active, they tend to stay in the shadows or hidden by thick vegetation. When observed, they commonly are sitting on a stump, log, or low branch.