A slough—also slow, slew, sloo, slue—is a narrow stretch of sluggish water in a river channel, inlet, or pond. A slough can also be a marsh, swamp, bayou, or any soft, muddy, or waterlogged ground. The great, ﬂat city of Chicago is built on ﬁlled sloughs, or swampy bottomlands. Slough is also a verb, meaning to mire in a slough or swamp, and “to be sloughed” can mean “lost in a swamp.” Used as slang, “to slough in,” or “slough up,” is to arrest or imprison, to be inhibited, or bogged down. Nineteenth-century travelers reported horses sinking up to their necks in sloughs that looked no deeper than a puddle. Prairies, especially those radiating from the Mississippi, are (or were) riddled with sloughs, and sloughs run along the St. Paul, Paciﬁc, and Sioux City Railroad tracks and other elevated rights-of-way, providing ideal homes for muskrats.