The northernmost end of the road lies at the very foot of the San Gabriel Mountains in Altadena and immediately accesses Las Flores Canyon. The first resident of Las Flores Canyon was the Forsyth Ranch. It sold in 1919 to Mr. Cobb who had an enormous and fascinating estate on the alluvial fan which emanates from the Canyon. Las Flores was also known for its small and short-lived gold mining operations there. The Cobb Estate was deeded to the United States Forest Service as a free growth Arboretum in 1967. The gates on Lake Avenue mark the entrance to the estate which still has its long, paved, curving driveway which leads to the site of the defunct manor. The adjacent trailhead of the Sam Merrill Trail also leads into the canyon from Lake Avenue. This is the origin of the local term "top of Lake," which refers to the northernmost neighborhoods.