Joseph S. Diller, a geologist, observed in 1915 that a "notable peculiarity" of the Santa Clara Valley is that "it is divided transversely by a scarcely noticeable soil-covered divide." The northern portion is drained northward by various rivers and creeks into San Francisco Bay. The southern portion of the valley is drained southward by Llagas Creek into the Pajaro River, which in turn flows westward to Monterey Bay. As one travels across the valley floor, "the alluvial plain is continuous across the divide." The summit of the transverse divide is about two miles from the former town of Madrone at an elevation of , but the alluvial plain is so continuous that most travelers are unaware they are crossing between two drainage basins.
