There are several types of puffballs in several genera. This one is Vascellum curtisii. Key features: the small size (2 cm), the prominent pyramidal spines that are easily rubbed off, and the round rather than pear shape. Habitat is also an important detail: this, unlike the closely related Lycoperdon marginatum, grows in grassy, disturbed areas. I found this growing on a bare patch of ground in our field. Mushrooms of the Midwest lists this as a late summer/fall species, but seasonality in mushrooms can be quite variable.
Puffballs are edible. But you should always cut them in half to make sure that they are pure white (like the one pictured here) and that the interior is solid rather than showing a developing cap-and-stem mushroom. If you do see something like that, you probably have a young (and potentially poisonous) Amanita.