Sea Lion Caves on the Oregon coast, 11 miles north of Florence along U.S. Highway 101, is a connected system of sea caves measuring 1,315 feet and recognized as the longest sea cave in the United States. Its main cavern, surf-washed at sea level beneath high cliffs, includes multiple openings and vividly colored rock walls. Over centuries, the cave and nearby rocks became the only known mainland rookery and hauling area for Steller sea lions, while also sheltering seabirds. Discovered in 1880 by Captain William Cox, the site was developed for public access in the early 20th century, opened in 1932, and expanded with an elevator in 1961, remaining a major wildlife viewpoint.