Snickerdoodles are a perfect example of the classic American cookie whose origins are a mystery. They've purportedly been around since Colonial times, and are thought of variously as a New England tradition, a Midwestern specialty, or a Pennsylvania Dutch legacy. The name snickerdoodle does have a faintly German ring to it–some conjecture that the "snicker" comes from "shnecken," for snail, and that the cookie may have been made in a coiled shape. But most likely, the name is sheer whimsy. Early incarnations of snickerdoodles sometimes contained nuts and raisins (or currants) but today's version is basically a sugar cookie with a little extra flavor; light, crisp-chewy and cinnamon-y.
Two hallmarks of a good snickerdoodle are its cinnamon coating and its tangy flavor. Drop-style snickerdoodle cookies are rolled in cinnamon sugar before baking; while they bake, they puff up and collapse, creating the distinctive crackled surface. There should be a lot of cinnamon in the sugar coating, not only for flavor but also for a nice visual contrast with the pale blonde cookie that shows through the cracks. As for the tangy flavor, that comes from cream of tartar. Cream of tartar is an acidic ingredient that reacts with alkaline baking soda to make the dough puff up. Some recipes instead use baking powder, which of course contains acid and alkaline ingredients mixed together. But these recipes miss the point, for besides its leavening abilities, the cream of tartar (which is made from grapes) lends a very slight sourness, which gives these cookies a unique taste.
The rolled cookie version below has a little less sugar and less egg, but is otherwise as close as you can get to real snickerdoodle dough while still being able to roll it out and cut it. To control the cookies' spread, this recipe (like some drop cookie recipes) uses shortening in place of some of the butter. A sprinkling of cinnamon sugar is all the cookies need in the way of embellishment.