Chipmunk, and 13 Lined Ground Squirrel. 2 different animals, frequently confused. Chipmunks actually carry themselves more like squirrels, than Ground Squirrels.
Ground Squirrels remind me of little sausages on legs. Their fur is shorter, and lays smoothly against them. They like to make their homes in flat, open, prairie-like areas, large lawns, and golf courses. Chipmunks tend to like edges of woods (savannas). Chipmunks are very good climbers. Their fur appears fluffier than Ground Squirrels.
Both Ground Squirrels, and Chipmunks have cheek pouches.
Photo 1 of Ground Squirrel from Field Herp Forum (Scott Waters).
Photo 2 Chipmunk in my yard