Area codes 510 and 341

The 1868 Hayward earthquake occurred in the San Francisco Bay Area, California, United States on October 21. With an estimated moment magnitude of 6.3–6.7 and a maximum Mercalli intensity of IX (Violent), it was the most recent large earthquake to occur on the Hayward Fault Zone. It caused significant damage and a number of deaths throughout the region, and was known as the "Great San Francisco earthquake" prior to the 1906 San Francisco earthquake and fire.

Eden Medical Center is a hospital and medical center located in Castro Valley, California, providing emergency medical services to Alameda County. It is operated by Sutter Health. It is built on an elevated area, and is visible from a distance.

Castro Valley is a census-designated place (CDP) in Alameda County, California, United States. At the 2010 census, it was the fifth most populous unincorporated area in California and the twenty-third most populous in the United States. The population was 66,441 at the 2020 census.Castro Valley is named after Don Guillermo Castro, a noted 19th-century Californio ranchero who owned the land where the community is located.

Ashland is a census-designated place (CDP) and unincorporated community in Alameda County, California, United States. The population was 23,823 at the 2020 census. Ashland is located between the city of San Leandro to the north, the unincorporated community of Cherryland to the south, the unincorporated community of Castro Valley to the east, and the unincorporated community of San Lorenzo to the southwest. Ashland shares a postal zip code with the neighboring unincorporated community of San Lorenzo to the southwest, as well as the close by cities of Hayward to the south and San Leandro to the north. There is no documented evidence that Ashland was ever known as “San Leandro South” but instead has been informally, albeit incorrectly, known as "unincorporated San Leandro" or "unincorporated Hayward" since Ashland does not have its own postal zip code designation.

Guadalupe Creek or Guadalupe Valley Creek is a short eastward-flowing stream whose watershed originates just east of the highest peak of San Bruno Mountain in San Mateo County, California, United States. It courses through San Bruno Mountain State and County Park and Brisbane before entering the Brisbane Lagoon.

Redwood High School is an alternative/continuation public high school in Castro Valley, California, United States. It is the only alternative/continuation high school in Castro Valley, and is one of only two high schools in Castro Valley, the other being Castro Valley High School. Redwood High School was remodeled from 2006 to 2008.

The Meek Mansion is a historic mansion in unincorporated Cherryland, California, just north of Hayward. It is listed on the National Register of Historic Places. Located on nearly 10 acres, the Victorian house was built in 1869 by William Meek.

Eden Congregational Church, also known as Pioneer Chapel, is a historic church building located just north of downtown Hayward in Alameda County, California. The building was listed on the National Register of Historic Places in 2007. The church is still in use by the Eden United Church of Christ (Congregational). A culverted stretch of San Lorenzo Creek runs past it.

Cherryland is an unincorporated community and census-designated place (CDP) in Alameda County, California, United States. Cherryland is located between Ashland to the north and the city of Hayward to the south. The population was 15,808 at the 2020 census.

Rancho San Lorenzo was a 26,722-acre (108.14 km2) Mexican land grant given in 1841 by Governor Juan Alvarado to Guillermo Castro a career soldier posted to the Pueblo of San José. The land grant included present day Hayward, San Lorenzo, and Castro Valley, including Crow Canyon, Cull Canyon, and Palomares Canyons.

Castro Valley High School is located in the unincorporated suburban community of Castro Valley, California, United States. It is a State school#United States high school for grades 9 to 12. Named a National Exemplary School in 1984–85 and 1988–89, it was a California Distinguished School in 1987–88, 2000–01, and 2009.It is part of the Castro Valley Unified School District.

John George Psychiatric Hospital, previously John George Psychiatric Pavilion, also known as John George Psychiatric Emergency Room, John George Hospital or John George, is a psychiatric hospital located in San Leandro, in Alameda County, California. It is operated by the Alameda Health System. It is located near Fairmont Hospital and the county Juvenile Justice Center. It opened in 1992 and was named after County Supervisor John George to honor his advocacy for mentally ill people. It has an 80-bed capacity. In November 2003, a doctor at the facility, Erlinda Ursua, died there and a patient, a 38-year-old female was charged with murder. The female patient pled not guilty in 2005. No criminal charges were later filed.