Siltcoos Lake (silt’-koos), at 3,164 acres, is the largest lake on the Oregon Coast of the United States. Fed by runoff from a basin of about 68 square miles in Douglas and Lane counties, it is located about 7 miles south of Florence and 0.5 miles east of U.S. Route 101. Its name comes from a Lower Umpqua (Siuslaw) placename, a variant of which is Tsiltcoos.