|Town of Hillsborough|
|— Town —|
Location in San Mateo County and the state of California
|- Total||6.2 sq mi (16.1 km2)|
|- Land||6.2 sq mi (16.1 km2)|
|- Water||0 sq mi (0 km2)|
|Elevation||322 ft (98 m)|
|- Density||1,746/sq mi (672.4/km2)|
|Time zone||PST (UTC-8)|
|- Summer (DST)||PDT (UTC-7)|
|GNIS feature ID||1659735|
Hillsborough is an incorporated town in San Mateo County, California, in the San Francisco Bay Area. Hillsborough is one of the wealthiest places in America and has the highest income of places in America with populations of at least 10,000. It is located seventeen miles (27 km) south of San Francisco on the San Francisco Peninsula, between Interstate 280 and SR 82 (El Camino Real). The population was 10,825 at the 2000 census. The town is served by Hillsborough City School District. Hillsborough is home to some of the Bay Area's wealthiest people, and the landscape is dominated by large homes; the city enforces a 2,500-square-foot (230 m2) minimum house size and half-acre minimum lot size to preserve exclusivity. As a result, there are no apartments, condominiums or townhouses in the city limits; however, it is not unusual for the homes along the eastern edge of Hillsborough to face condominiums in neighboring Burlingame, with which it shares ZIP code 94010. In 2007, Coldwell Banker lists Hillsborough as the most expensive housing market in the United States, with a median home price of over $3.8 million.
Hillsborough is located on the Rancho San Mateo Mexican land grant which was purchased by William Davis Merry Howard, son of a wealthy Hillsboro, New Hampshire shipping magnate, in 1846. Howard settled his family in this area, which attracted wealthy San Franciscans. In 1910, Hillsborough residents voted to incorporate.
Hillsborough is located at .
According to the United States Census Bureau, the town has a total area of 6.2 square miles (16.1 km²), all of it land. The area's hilly topography and lack of use of a grid layout for roads make navigation by outsiders notoriously difficult. The area of Crystal Springs Road is one of the most difficult to navigate.
There are two prominent streams that drain the mostly wooded slopes of Hillsborough: San Mateo Creek and Cherry Creek. In both cases the upper watersheds are closed canopy California oak woodlands, with dominant trees of Coast Live Oak, Pacific Madrone and California Bay.
The upper drainage area of San Mateo Creek in Hillsborough contains significant serpentinite outcrops, which are known habitats for several rare plant species including the San Mateo Woolly Sunflower. Other common plants include Toyon, gooseberry, lupine, monkeyflower and coffeeberry. Commonly observed mammals include California Mule Deer, raccoon, opossum and skunk.
Hillsborough is bordered to the west by Interstate 280, and to the south by Crystal Springs Road which runs along San Mateo Creek. The San Mateo Highlands borders Hillsborough to the south across San Mateo Creek.
As of the census of 2000, there were 10,825 people, 3,689 households, and 3,161 families residing in the town. The population density was 1,738.7 people per square mile (670.9/km²). There were 3,804 housing units at an average density of 611.0/sq mi (235.8/km²). The racial makeup of the town was 71.80% White, 24.04% Asian, 2.67% from two or more races, 0.70% from other races, 0.50% African American, 0.23% Pacific Islander, and 0.06% Native American. Hispanic or Latino of any race were 2.81% of the population.
There were 3,689 households out of which 36.3% had children under the age of 18 living with them, 78.6% were married couples living together, 4.9% had a female householder with no husband present, and 14.3% were non-families. 11.1% of all households were made up of individuals and 7.3% had someone living alone who was 65 years of age or older. The average household size was 2.93 and the average family size was 3.14.
In the town the population was spread out with 25.1% under the age of 18, 4.4% from 18 to 24, 19.7% from 25 to 44, 32.2% from 45 to 64, and 18.6% who were 65 years of age or older. The median age was 46 years. For every 100 females there were 94.6 males. For every 100 females age 18 and over, there were 91.6 males.
The median income for a household in the town was $193,157, and the median income for a family was $200,000. Full-time male workers have a median income of $100,000+ versus $55,882 for full-time female workers. The per capita income for the town was $98,643. About 1.8% of families and 2.8% of the population were below the poverty line, including 2.7% of those under age 18 and 0.8% of those age 65 or over.
In the state legislature Hillsborough is located in the 8th Senate District, represented by Democrat Leland Yee, and in the 19th Assembly District, represented by Democrat Gene Mullin. Federally, Hillsborough is located in California's 12th congressional district, which has a Cook PVI of D +22 and is currently represented by Democrat Jackie Speier.
Primarily a residential suburb of San Francisco, Hillsborough has many mansions within the town's borders dating from the early 20th century.
December is the coolest month with an average high of 60 degrees, and September is the warmest month with an average high of 73 degrees. Hillsborough has a Mediterranean climate (Köppen climate classification Csa), with the majority of the precipitation from the months of November to April, with often times 0.0 inches precipitation from May to October. On average, Hillsborough receives 20 inches of rain. However, it is extremely rare to have an average year of rainfall, usually, there are 3–5 years of 10-12 inches of rain, with one year which receives 35+ inches of rain often with over 20 inches in 1 month. With mountains to the west of Hillsborough, it is blocked from much of the rainfall over Half Moon Bay, and also is blocked from virtually all the fog of the coast. Hillsborough receives 300 days of sunshine, with 50 days of recordable precipitation a year.