Mount Wilson is one of the better known peaks in the San Gabriel Mountains, part of the Angeles National Forest in Los Angeles County, California. It is the location of the Mount Wilson Observatory and has become the astronomical center of Southern California with 60-inch (1,524 mm) and 100-inch (2,540 mm) telescopes, and 60-foot (18.3 m) and 150-foot (45.7 m) tall solar towers. The summit is at 5,710 feet (1,740 m). Some surrounding peaks are slightly higher. Due to its elevation, snow can sometimes interrupt astronomical activities on the mountain.
The native inhabitants of the San Gabriel's probably belonged to various tribes of the Tongva people who lived in the low-lying valleys. Granite outcroppings along the Angeles Crest show signs of meal preparations with metate pots ground into rock surfaces.
The first recorded exploration of the mountain was performed by Benjamin Davis Wilson also known as "Don Benito". Wilson, who was the grandfather of George S. Patton, Jr., was the owner of Rancho San Pascual in about 1852 and ran a winery at his home, "Lake Vineyard", which was in the area of today's San Marino. Wilson hoped to find a suitable wood for his casks but was disappointed by the poor quality of trees on the mountain. He built a trail, following an established Indian route, which became known as the Mount Wilson Trail. In turn Wilson's trail became the predecessor of the Mount Wilson Toll Road. He was surprised to find line shacks at the summit, probably left by Spaniards who were known to track down destructive grizzly bears. He built a three-room cabin along the trail called "Halfway House." Despite Wilson's inability to find adequate wood, the hike became a popular pastime for locals who would make a weekend trip to the summit. These hikers built signal fires on the summit to let people below know that the party had arrived safely.
In 1889 Professor William Pickering of Harvard University along with Alvan P. Clark, famous lens grinder, prepared an experiment with a 4-and-13-inch (102 and 330 mm) telescopes at Mount Wilson. University students would operate the telescopes for nighttime viewing, but more often than not they would log in "bad weather, no visibility" and head to town to relieve their boredom. The small observatory was abandoned with plans to build a larger one at a later date.
In 1891 Prof. Thaddeus S. C. Lowe incorporated the Pasadena & Mount Wilson Railroad with the plan of building a scenic mountain railroad to the summit of Mt. Wilson. At the same time land and easement disputes between camp owners Steils and Strain were going on over the public and private use of the Mount Wilson Trail. The courts ruled that the trail was a public thoroughfare and that any blockading would be illegal. At the foot of the mountain, a local contractor Thomas Banbury built a 10-mile (15 km) roadway to be named "The New Mount Wilson Trail," aka "The Mount Wilson Toll Road." Passage fare was 25¢ round trip for hikers and 50¢ for horseback.
In 1892 Prof. Charles William Eliot, president of Harvard University, planned to have two 40-inch (102 cm) lenses shipped from Alvin Clark and Sons in Corning, New York to the newly named Mount Harvard, directly adjacent to Mt. Wilson. The money was to be put up by Mr. Spence of the University of Southern California. Walter Raymond, of Raymond & Whitcomb Travel Agency, Boston, and owner of the Raymond Hotel, Pasadena, offered to pay for rail from New York. Lowe offered to take the lenses up via his yet-to-be-built Mt. Wilson Railway. Spence died suddenly and left no word of the money for the project. The lenses ended up at Yerkes Observatory in Wisconsin, and Lowe's railway ended up going to Oak Mountain (Mount Lowe).
By 1901 The Mount Wilson Toll Road Co. had purchased Henninger Flats, Strain's Camp, Martin's Camp, and 640 acres (2.6 km²) of the summit.
In 1903 George Ellery Hale visited Mt. Wilson only to become so enthused by the perfect conditions for which to set up an observatory, which would become the Mount Wilson Observatory. In 1905 40 acres (160,000 m2) were leased for 99 years by the Carnegie Institute for telescopes, and construction began on a new Mt. Wilson Hotel. In 1908 a 60-inch (1524 mm) telescope was installed at the summit, and in 1910 the 150-foot (46 m) tall Solar Tower was erected. In 1913 the hotel burned down and was replaced by a second hotel that lasted until its demolition in 1966. The Toll Road opened to automobiles in 1912 and lasted until 1936.
In 1926 Albert Abraham Michelson made what was the most precise calculation of the speed of light at the time by measuring the round-trip travel time of light between Mount Wilson and Mount San Antonio 22 miles (35 km) away.
In 1948 the first radio/television antenna was installed with more soon to follow. So popular became the Mt. Wilson site that the Metromedia Company bought 720 acres (2.9 km2) of the Mount Wilson Hotel Company. The Hotel was replaced with Skyline Park that closed in 1976 after having gone through almost a decade of operating in the red.
The Mount Wilson Electronics Reservation consists of numerous radio and television transmitters serving the Greater Los Angeles Area, together with microwave relay facilities used by AT&T and other entities. The roads in the Electronics Reservation consist of two one-way loops, although it is common to encounter oncoming traffic. The loop roads were closed for public access between 2006 and 2009.
The tallest tower on Mount Wilson, according to FCC database, is the guyed mast of KCBS-TV at a height of 972 feet (296.3 m), built in 1986.
In 1984 the Carnegie Institute began the process of shutting down the observatories on Mt. Wilson, opting to concentrate on newer sites in Chile. But in 1986 the Mt. Wilson Institute was formed and plans to reopen the observatories were made so that by 2000 all the telescopes were back in operation.
Construction began in 1996 for six 1-meter telescopes by the Center for High Angular Resolution Astronomy at Georgia State University. This is the largest optical interferometric array ever built. The telescopes were installed in 1999 and the facility became operational by 2001.
The evening of August 30, 2009 as of 10pm PDT (0500 GMT), the Station Fire is currently threatening the tower cluster and the Observatory, along with nearby Mount Harvard. Two firefighters headed up the mountain were killed in a rollover accident. . Three others suffered serious injuries due to ignoring evacuation orders. This led Governor Schwarzenegger to make a plea to the public to abide by evacuation orders.