Mount Hamilton is a mountain in California's Diablo Range. In 1861, while working for Josiah D. Whitney on the first California Geological Survey, William H. Brewer invited local San Jose preacher (and Brewer's personal friend) Laurentine Hamilton to join his company on a trek to a nearby summit. Nearing completion of their journey, Hamilton, in good humor, bounded for the summit ahead of the rest of the men and claimed his stake. In fact, Brewer suggested the mountain be named after Hamilton only after Whitney declined to have the mountain named after him (a different mountain was later named Mount Whitney).
Mount Hamilton is the tallest mountain overlooking Silicon Valley, and is the site of Lick Observatory, the first permanently occupied mountain-top observatory. The various summits along its mile-long summit ridge have been given astronomy-related names. The highest is Copernicus Peak at 4360+ feet (1329+ m). 4,250-foot (1,295 m) Kepler Peak and 4,213-foot (1,284 m) Observatory Peak follow. The latter was more than 30 feet (9.1 m) taller before it was leveled during the construction of the observatory in the 1880s. The asteroid 452 Hamiltonia, discovered in 1899, is named after the mountain. Golden Eagle nesting sites are found on the slopes of Mount Hamilton.
These mountains are high enough to receive snowfall in the winter, perhaps up to a dozen times. Occasionally, when a cold, wet storm comes in from the Gulf of Alaska or Canada, Mt. Hamilton and the surrounding peaks get serious snowfall. In February 2001, 30 inches (76 cm) of snow fell, and in March 2006, the peak was left with over a foot (30 cm) of snow in one night.
The National Weather Service has had a cooperative weather station on the summit of Mount Hamilton almost since the time that the Lick Observatory opened. It has provided a glimpse of the extreme weather conditions that occur on the Diablo Range, especially in the winter months.
January is usually the coldest month on Mount Hamilton with an average high of 49.4 °F (9.7 °C) and an average low of 37.5 °F (3.1 °C). The warmest month is usually July with an average high of 78.2 °F (25.7 °C) and an average low of 63.1 °F (17.3 °C). Due to frequent thermal inversions during the summer, it is often warmer on Mount Hamilton than in San Jose. The record high temperature of 103 °F (39 °C) was on August 5, 1978. The record low temperature of 7 °F (−14 °C) was on December 21, 1990. The average days with highs of 90 °F (32 °C) or higher is 4.3 days. The average days with lows of 32 °F (0 °C) or lower is 50.6 days.
Annual precipitation averages 23.73 inches (603 mm). Measurable rainfall occurs on an average of 71.9 days each year. The most rainfall in a month was 12.13 inches (308 mm) in February 1998; no rainfall has been common during the summer months. The maximum rainfall in 24 hours was 6.87 inches (174 mm) on December 23, 1955.
Annual snowfall averages 10 inches (25 cm). The maximum snowfall in a year was 59.0 inches (150 cm) in 1955. The maximum snowfall in a month was 33.6 inches (85 cm) in January 1950. The 24-hour maximum snowfall of 14.0 inches (36 cm) occurred on February 18, 1990. The deepest daily snow depth was 18 inches (46 cm) in March 1976. Measurable snow has been recorded in every month from November through June.
|Weather data for Mount Hamilton, California|
|Average high °F||49.4||49.6||50.4||55.8||63.4||72.0||78.2||77.9||73.8||65.3||53.9||49.9||61.6|
|Average low °F||37.5||36.9||37.0||40.0||46.8||55.3||63.1||62.8||58.2||50.8||41.0||37.3||47.2|
|Average high °C||9.7||9.8||10.2||13.2||17.4||22.2||25.7||25.5||23.2||18.5||12.2||9.9||16.4|
|Average low °C||3.1||2.7||2.8||4.4||8.2||12.9||17.3||17.1||14.6||10.4||5.0||2.9||8.4|
The sinuous 19-mile (31 km) Mt. Hamilton Road (part of State Route 130) is popular with bicyclists and motorcyclists. Built in 1875–76 in anticipation of the observatory, and the need to carry materials and equipment up the mountain in horse-drawn wagons, the grade seldom exceeds 6.5 percent. The road rises over 4,000 feet (1,200 m) in three long climbs from San Jose to the mountain top. Cyclists fondness for the road relate to the long but not overly challenging nature of the climb, sparse vehicular traffic over most of its length, and spectacular views of San Jose and the rest of the Santa Clara Valley below. There is an annual cycling challenge climb in April. Thanksgiving consistently draws hundreds of cyclists and is frequently the final climb in the annual Low-Key Hillclimb Series which attracts some of the region's best climbers.
Strong regional climbers can attain the peak in 70–80 minutes starting from Alum Rock Road. On a clear day at the summit it is possible to see the Sierra Nevada. These views do not come without a price, as numerous accidents occur on the road each year. Whenever it snows on Mount Hamilton, the road is closed until crews can clear the road of snow and black ice.
The 20-mile (32 km) drive from Interstate 680 to Lick Observatory takes about 45 minutes.
The bicycle ride is just over 19 miles (31 km) from the Alum Rock Road junction. The upward trek is interrupted by two descents, first into Grant Ranch County Park, and again to cross Smith Creek. Quimby Road offers a shorter way from San Jose to Grant Ranch, but is considerably steeper. The main observatory building has water, a few vending machines, restrooms, and an opportunity to warm up on a cold day. If the time is right, there are also free 15-minute guided tours of the Great Lick refracting telescope, and the gift shop may be open.
The road is advertised to include 365 curves, one for each day of the year. This is true, subject to definition of the term "curve." If the yellow line bends to the right, then straightens out, then bends to the right again, it is regarded as one curve. If the yellow line describes an ess, on the other hand, it counts as two curves, regardless of how gentle the ess may be.
The road continues, as the San Antonio Valley Road, down the backside of Mount. Hamilton, through almost completely empty country, and eventually comes out at Patterson, in Stanislaus County. Shortly after the summit, one can turn to the north and proceed on Old Mines Road, which ends at Livermore. There are ranches, farms, several cattle gates along this road, and even a (paved) ford through a shallow stream. Traffic is light to nonexistent.
Much of the foothill slopes of Mount Hamilton is underlain by Miocene age sandstone of the Briones formation: this bedrock is locally soft and weathered in the upper few feet, but grades locally to very hard at depth. Depth to groundwater on these foothill areas of Mount Hamilton is approximately 240 feet (73 m). The Babb Creek drainage comprises some of the watershed draining the slopes of Mount Hamilton. The Calaveras and Hayward active earthquake faults traverse the slopes of Mount Hamilton.
Mount Hamilton has its own zip code, 95140; it is generally uninhabited open space with a population in 2000 of only 35. The place also has its own police force (one officer, a member of the University of California police), but because there were not enough school-age children in 2006, the Mount Hamilton Elementary School has been close.