Since its founding in 1971, the San Diego Association of Geologists (SDAG) has published annual volumes and selected geoscience works on the San Diego region and adjacent areas of southern and Baja California. Each volume helps professional geoscientists and students, as well as natural history enthusiasts, discover and understand specific areas and aspects of their land via self-guided field trips, scholarly and popular papers, and maps and photographs. This volume, named for the traverse across the region's mountainous spine, explores yet another aspect of little-known features of coastal attractions familiar to millions and "roads less traveled" along Old Highway 80 to the Yuha Desert and San Andreas fault in Imperial County, linking SDAG field trips and volumes along a corridor from sea to desert.