At the mouths of rivers where freshwater and seawater mingle, the effects of tides are evident and often dramatic. In shallow stretches alternately ﬂooded at high tide and drained at low tide, salt grass thrives. In the low tide pools where water always stands, cordgrass (Spartina) grows in the changing salinity, temperature, and water level. But salt grass (Distichlis) tends to prefer the higher, radically ﬁlling and emptying stretches of the estuary. In a salt-grass estuary the grass holds only some of the ﬁne particles of clay and silt laid down by the shifting currents, its roots and stems lacing the soft mud. The salt grass protects the shore by buffering the force of wind and tides. The dying grass also provides for the inhabitants of the estuary such as snails and periwinkles, oysters and ﬁddler crabs, which in turn feed many birds and animals. Salt-grass estuaries are primarily features of the eastern United States. North Carolina has more square miles of estuary than any other state. Different water levels, tidal patterns, salinity, temperature, and variations in sediment make each basin and salt grass meadow different. Early immigrants to New England sometimes settled near estuaries hoping to harvest salt grass for hay, but were disappointed when cows and horses did not care for the salty fodder.