Mima mounds are sometimes called pimple mounds and vice versa, but the two formations are geographically and geologically distinct. Mima mounds derive their name from the Mima Prairie, near Olympia, Washington, where they abound. They occur in dry, grassy upland areas of the West. They are up to six feet high and up to 30 feet across. They are often attributed to the subterranean exertions of pocket gophers, over many generations. Writing from southern California, Alfred Wallace advises ﬁlling a shallow pan with eggs, lying on their sides and with their axes unaligned, then pouring ﬁne sand into the pan until the eggs are half buried. This, he says, “gives a fair representation” of a mima plain. Such plains are colloquially called hog wallows. One presumes some poetic soul saw the low mounds and thought of recumbent swine.