Cajon Pass

Cajon Pass (/kəˈhoʊn/; Spanish: Puerto del Cajón or Paso del Cajón) is a mountain pass between the San Bernardino Mountains to the east and the San Gabriel Mountains to the west in Southern California. Created by the movements of the San Andreas Fault, it has an elevation of 3,777 ft (1,151 m). Located in the Mojave Desert, the pass is an important link from the Greater San Bernardino Area to the Victor Valley, and northeast to Las Vegas. The Cajon Pass area is on the Pacific Crest Trail.

Cajon Pass is at the head of Horsethief Canyon, traversed by California State Route 138 (SR 138) and railroad tracks owned by BNSF Railway and Union Pacific Railroad. Improvements in 1972 reduced the railroad's maximum elevation from about 3,829 to 3,777 feet (1,167 to 1,151 m) while reducing curvature. Interstate 15 does not traverse Cajon Pass, but rather the nearby Cajon Summit, 34°20′58″N 117°26′47″W / 34.34944°N 117.44639°W / 34.34944; -117.44639 (Cajon Summit)^{[citation needed]}. The entire area, Cajon Pass and Cajon Summit, is often referred to as Cajon Pass, but a distinction is made between Cajon Pass and Cajon Summit.

In 1851, a group of Mormon settlers led by Amasa M. Lyman and Charles C. Rich traveled through Cajon Pass in covered wagons on their way from Salt Lake City to southern California. A prominent rock formation in the pass, where the Mormon Road and the railway merge (at 34°19′06″N 117°29′31″W / 34.3184°N 117.4920°W / 34.3184; -117.4920, near Sullivan's Curve), is known as Mormon Rocks.

In Spanish, the word cajón refers to a box or drawer. The name of the pass is derived from the Spanish land grant encompassing the area; it was first referred to in English on an 1852 map. Early Latter-day Saint documents, which often referred to the pass as "Cahoon Pass", suggest an alternate explanation for the name, that it is named in honor of Mormon pioneer Andrew Cahoon (pronounced similarly to Cajon), who was an early settler in nearby San Bernardino and assisted in surveying and laying out the city of San Bernardino.

Cajon Pass is known for high wind, turbulence and fog. The weather over the pass can vary from foggy days with poor visibility to clear afternoons where aircraft are bounced by gusting Santa Ana winds that top 80 mph (130 km/h). The wind is typically from the west, although in Santa Ana and other weather conditions it may be out of the north or the southeast. Air spilling over the San Gabriels can cause violent up- and downdrafts. On a normal day, with the wind out of the west, turbulence usually starts a few miles west of Rialto and continues a few miles to the east, growing in strength above the altitude of the mountains and especially over the pass near the HITOP intersection. In Santa Ana conditions, up- and downdrafts can become violent northeast of Ontario Airport, and turbulence can be experienced east to the Banning Pass, well known for turbulence. The mass and wing loading of an aircraft determine its sensitivity to turbulence, so what may seem violent in a Cessna 172 may seem only mild to moderate in a Boeing 747. In the 2006 Mercy Air 2 accident, an air ambulance helicopter collided with mountainous terrain near the pass in foggy weather.

The California Southern Railroad, a subsidiary of the Atchison, Topeka and Santa Fe Railway, was the first railroad through Cajon Pass. The line through the pass was built in the early 1880s to connect the present day cities of Barstow and San Diego. Today the Union Pacific Railroad and BNSF Railway (the successor to the Santa Fe) use the pass to reach Los Angeles and San Bernardino as part of the Southern Transcon. Due to the many trains, scenery and easy access, it is a popular location for railfans, and many photographs of trains on Cajon Pass appear in books and magazines.

The Union Pacific Railroad owns one track through the pass, on the previous Southern Pacific Railroad Palmdale cutoff, opened in 1967. The BNSF Railway owns two tracks and began to operate a third main track in the summer of 2008. The railroads share track rights through the pass ever since the Union Pacific gained track rights on the Santa Fe portion negotiated under the original Los Angeles and Salt Lake Railroad. The original BNSF (ATSF) line was built in the 1880s and later roads, U.S. Route 66 and I-15, roughly followed this route. The 3.0% grade for a few miles on the south track is challenging for long trains, making the westbound descent dangerous, as a runaway can occur if the engineer is not careful in handling the brakes. The second track, built in 1913, is 2 miles (3.2 km) longer to get a lower 2.2% grade. It ran through two short tunnels, but both were removed when the third main track was added next to the 1913 line. Trains may be seen traveling at speeds of 60 and 70 mph (97 and 113 km/h) on the straighter track away from the pass, but typically ascend at 14 to 22 mph (23 to 35 km/h) and descend at 20 to 30 mph (32 to 48 km/h). With the third track, the BNSF lines have a capacity of 150 trains per day.

Amtrak's Desert Wind used the pass until it quit running in 1997. The Southwest Chief runs daily between Chicago and Los Angeles, through Cajon Pass on the BNSF line.