Historical sources indicate that, in the late 19th century, the portion of the southern California coastline between Palos Verdes Peninsula and San Mateo Point was composed of a series of barrier spits backed by estuaries, beaches backed by cliffs, and occasional rocky headlands. Nearly natural conditions, a reflection of minimal human impact, prevailed during this relatively stormy interval. US Coast [and Geodetic] Survey materials, early scientific work, newspaper articles, and the accounts of travelers provide much of the information utilized to reconstruct the shoreline. Serving as a major roadway, the beach that extended between San Juan Creek and San Mateo Creek was especially well known. The barrier spits were capped by low dunes and were separated by migrating inlets connecting the ocean with the backing estuaries. Rivers discharged into the estuaries at times, decreasing salinities and depositing sediments. Rocky coastlines are believed to have experienced substantial erosion as high levels of bioerosion and vigorous attack by storm waves is inferred, giving rise to notched cliffs, sea caves, and other erosional forms. Forming part of the seaward fringe of the greater Los Angeles region, today this shoreline is completely developed, serving the commercial and recreational needs of millions of residents and visitors.