Angeles, more or less along the present route of Interstate 10, helped further open agriculture, commerce and tourism to the rest of the country. So too did the coming of State Highway 111 in the early 1930s, which cut a diagonal swath through the valley and connected all of its major settlements. Dr. June McCarroll, then a nurse with the Southern Pacific whose office fronted U.S. 99 in Indio, is credited with being the first person to delineate a divided highway by painting a stripe down the middle of the roadbed in response to frequent head-on collisions. The standard was refined and adopted worldwide. Doctor McCarroll is memorialized by a stretch of I-10 through Indio named in her honor. The Coachella Valley became popular among celebrities from Frank Sinatra to Dakota Fanning who came to enjoy vacations and winter homes in the desert resort community. It became a real estate destination in the 1980s and 1990s and has also become a tourist attraction. Geography The Coachella Valley is the northernmost extent of the vast Salton Trough, also called the Cahuilla Basin, which includes the Salton Sea, and the Imperial Valley in the United States, as well as the Mexicali Valley and Colorado River Delta in Mexico. The trough is a result of combined tectonic activity of the San Andreas Fault, which follows the northeastern side of the valley, and the East Pacific Rise that runs up through the Gulf of California to the Salton Sea. The area is surrounded on the southwest by the Santa Rosa Mountains, by the San Jacinto Mountains to the west, the Little San Bernardino Mountains to the east and San Gorgonio Mountain to the north. These mountains peak at around and tend to average between . Elevations on the Valley floor range from above sea level at the north end of the Valley to below sea level around Mecca. The San Andreas Fault traverses the Valley's east side. Because of this fault, the Valley has many hot springs. The Santa Rosa Mountains to the West are part of the Elsinore Fault Zone. The results of a prehistoric sturzstrom can be seen in Martinez Canyon. The Painted Canyons of Mecca feature smaller faults as well as Precambrian, Tertiary and Quaternary rock formations, unconformities, badlands and desert landforms. Fault lines cause hot water springs or geysers to rise from the ground. These natural water sources made habitation