Stillwater is a term that describes a curious phenomenon of quiet water. In the United States over two hundred places are named Stillwater— including rivers, canyons, streams, ponds, even ﬂats and towns. In the late seventeenth century one such town, bordered by the Hudson River near Saratoga, New York, was chronicled as a place where “the water passes so slowly as not to be discovered, while above and below it is disturbed, and rageth as in a great sea, occasioned by rocks and falls therein.” In the late 1800s the best-known city by this name, Stillwater, Oklahoma, formed near a back-eddied place on a creek. Lesser-known Stillwater towns in Nevada, Montana, and elsewhere also grew up around pools of tranquil water. Such cities, because of their names, are often presented as stereotypically tranquil places to live, as depicted in Richard and Florence Atwater’s Mr. Popper’s Penguins: “It was an afternoon in late September. In the pleasant city of Stillwater, Mr. Popper, the house painter, was going home from work.” Stillwater is a term also used by meteorologists in predicting storm surges. In deep water they look for the midpoint of the wave crest before it reels down; in shallow water they look for the trough and crest of the wave. The stillwater level is the highest water level measured if wave action were completely smoothed out.