Hillsborough

According to the United States Census Bureau, the town has a total area of 6.2 square miles (16 km2), all of it land. The area’s considerably winding, hilly topography, and impossibility of a grid layout make Hillsborough notoriously challenging to navigate. Many lots include fairly steep slopes, particularly the western side of the town, with the landscape generally flattening to the east as it descends from the 280 freeway to El Camino Real and the towns of Burlingame and San Mateo.

Two prominent streams 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, raccoons, opossum, coyotes, rabbits, squirrels, and skunks.

Hillsborough is bordered by Burlingame to the north, San Mateo to the east, Highlands-Baywood Park to the south, and Interstate 280 to the west.

Hillsborough’s landscape is dominated by large homes; the town zoning and subdivision ordinances require a 2,500-square-foot (230 m2) minimum house size and minimum lot size of 0.5 acres (2,000 m2). 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, sharing the ZIP code 94010.

The town has no commercial zoning and thus no businesses within the town limits; the only non-residential properties are the town’s four public and three private schools, town and county government facilities, a golf course, a country club, and small parks.

Hillsborough has its own highly regarded and -ranked public elementary and middle school system, but no public high school. High school-aged children can attend one of several schools in the San Mateo Union High School District, generally assigned by residential address. The town is also home to a small number of independent schools. The Hillsborough school district is ranked as the #1 school district in California and one of the top ten school districts in the country.

• The Nueva School, a nationally recognized independent school serving gifted and talented students.
• Crocker Middle School, a public middle school, located on Ralston Avenue, named after William H. Crocker.
• West Elementary School, a public elementary school, located on Barbara Way.
• South Elementary School, a public elementary, at 303 El Cerrito.
• North Elementary School, a public elementary, at 545 Eucalyptus Avenue.
• The Bridge School, a school serving students with physical and speech impairments.
• Crystal Springs Uplands School, a college preparatory middle and high school.

Primarily a residential suburb of San Francisco, Hillsborough has many mansions and other points of interest within the town’s borders dating from the early 20th century.

• Carolands — Built by Harriet Pullman Carolan, heiress to the Pullman railway. At 65,000 ft² (6,000 m²), it is one of the largest residences in the United States and is placed on the National Register of Historic Places.
• ′The Flintstone House′ (a.k.a. the Adobe/Dome/Bubble/Marshmallow/Gumby house) — designed by architect William Nicholson and built in 1976 using sprayed concrete over balloon-shaped forms, now painted a deep/burnt orange color reminiscent of the Golden Gate Bridge’s distinctive hue. The house can be seen to the east from the Doran Memorial Bridge, northbound on Highway 280 between the Bunker Hill and Hayne/Black Mountain exits.
• Skyfarm — Built by William H. Crocker, namesake of Crocker middle school, and grandson of Charles Crocker of California’s Big Four railroad magnates. Designed by Arthur Brown, Jr., and opened in 1930. Home since the 1960s to The Nueva School.
• Tobin Clark Estate – Originally designed by the noted architect David Adler for Mrs. Celia Tobin Clark, one of the Peninsula’s most prominent families of the early 20th Century
• Uplands — Built by Templeton Crocker, as a gift to his fiancée Helène Irwin, heiress to the C&H Sugar family fortune. Designed by Willis Polk; opened in 1912, with interior of 35,000 ft² (3,250 m²). Home since the 1950s to Crystal Springs Uplands School.
• Western White House — Commissioned by George Randolph Hearst, son of William Randolph Hearst and now privately owned. It, like Hearst Castle was designed by Julia Morgan.
• Junípero Serra statue — Overlooking Highway 280, the statue was built in honor of Father Junípero Serra.

December is the coolest month with an average high of 60 degrees, and September is the warmest month with an average high of 78 degrees. Hillsborough has a Mediterranean climate (Köppen climate classification Csa), with the vast majority of the precipitation from the months of November to April. On average, Hillsborough receives 17 inches (430 mm) of rain. With coastal mountains to the west of Hillsborough, it is blocked in the winter from much of the rainfall over Half Moon Bay, and in the summer it is blocked from virtually all the fog of the coast. Hillsborough receives an average of 307 days of sunshine annually, with 52 days of recordable precipitation per year.