The following important events in the history of California affected political boundaries, record keeping, and family movements.
- 1542-1812: Spain, Mexico, England, and Russia made various claims to California, but most settlements were Spanish.
- 1769: The first permanent settlement was made by the Spanish in the San Diego Bay area.
- 1821: Spain granted Mexico its independence. California was included with Mexico.
- 1841: Americans began traveling overland to California.
- 1846: War broke out between the United States and Mexico. U.S. settlers in California set up a republic.
- 1848: Mexico ceded California to the United States. Gold was discovered at Sutter's Mill.
- 1849: The Gold Rush attracted over 100,000 people to California.
- 1850: ( September 9,) California became the 31st state
- 1851-52: California Indian Wars
- 1860-1861: (23 April-24 October) Pony Express
- 1869: Completion of the transcontinental railroad gave California a direct connection with the East. Great numbers of Chinese were imported to work on this railroad.
- 1872: The Modoc War on border between Oregon and California, between the U.S. and the Modoc tribe led by Chief Kintpuash (Captain Jack), the tribe had ceded their land in 1864, they were sent to the Klamath reservation, in 1870 they returned to their old land. 1873 the remaining tribal members sent to Oklahoma.
- 1884-1885: A railroad rate war (1884) and a California real estate boom (1885) caused a new wave of overland immigration.
- 1917–1918:More than 26 million men from the United States ages 18 through 45 registered with the Selective Service. World War I over 4.7 million American men and women served during the war.
- 1930's: The Great Depression closed many factories and mills. Many small farms were abandoned, and many families moved to cities.
- 1940–1945: Over 50.6 million men ages 18 to 65 registered with the Selective Service. Over 16.3 million American men and women served in the armed forces during World War II.
- 1950–1953: Over 5.7 million American men and women served in the Korean War.
- 1950's–1960's The building of interstate highways made it easier for people to move long distances.
- 1964–1972: Over 8.7 million American men and women served in the Vietnam War.
Histories are great sources of genealogical information. Many contain biographical information about individuals who lived in the area, including:
Some of the most valuable sources for family history research are local histories. Published histories of towns, counties, and states usually contain accounts of families. They describe the settlement of the area and the founding of churches, schools, and businesses. You can also find lists of pioneers, soldiers, and civil officials. Even if your ancestor is not listed, information on other relatives may be included that will provide important clues for locating your ancestor. A local history may also suggest other records to search. Local histories are extensively collected by the Family History Library, public and university libraries, and state and local historical societies. Three useful guides are:
- California Local History: A Bibliography and Union List of Library Holdings is a bibliography of local histories for California 
State Histories Useful to Genealogists
Good genealogists strive to understand the life and times of their ancestors. In this sense, any history is useful. But certain kinds of state, county, and local histories, especially older histories published between 1845 and 1945, often include biographical sketches of prominent individuals. The sketches usually tend toward the laudatory, but may include some genealogical details. If these histories are indexed or alphabetical, check for an ancestor's name. The Family History Library has numerous state and local histories by James M. Guinn and other authors. Sources for studying the history of California include:
The Family History Library has numerous state and local histories by James M. Guinn and other authors. Sources for studying the history of California include:
- History of California.  There is an index in 979.4 B4b which covers 1542 to 1859.
- A History of California: The Spanish Period 
- California and Californians  Volumes 3 and 4 contain biographical material. All four volumes are online at Ancestry.com. ($)
United States History
The following are only a few of the many sources that are available:
- The Almanac of American History,   This provides brief historical essays and chronological descriptions of thousands of key events in United States history.
- Dictionary of American History, Revised ed   This includes historical sketches on various topics in U.S. history, such as wars, people, laws, and organizations. A snippet view is available at Google books.
- Webster's Guide to American History: A Chronological, Geographical, and Biographical Survey and Compendium    This includes a history, some maps, tables, and other historical information.
To find more books and articles about California's history use the Internet Google search for phases like "California history." Family History Library Catalog Surname Search lists many more histories under topics like:
- CALIFORNIA- HISTORY
- CALIFORNIA. [COUNTY] - HISTORY
- CALIFORNIA, [COUNTY], [TOWN] - HISTORY
- CALIFORNIA, BIBLIOGRAPHY
- California Historical Society
- California History
- History of California - Wipedia
- The State of California's History Site
- Margaret M. Rocq, California Local History: A Bibliography and Union List of Library Holdings, 2nd ed. (Stanford, Calif.: Stanford University Press, 1970; FHL book 979.4 H23r; supplement, 1961 to 1970, is 979.4 H23r Supp.; 1950 ed. is on film 1000136 item 3 is on film 1000136 item 3).
- Filby, P. William. A Bibliography of American County Histories. Baltimore: Genealogical Publishing, 1985. (FHL book 973 H23bi)
- Kaminkow, Marion J. United States Local Histories in the Library of Congress. 5 vols. Baltimore: Magna Charta Book, 1975-76. (FHL book 973 A3ka.)
- Bancroft, Hubert H. ed. History of California. Six Volumes. San Francisco, California: A. L. Bancroft and Company, 1884-90. (Family History Library book 979.4 B4b Volumes 1-6; film 982473 items 1-2, Volumes 1-2; items 3-5, Volumes 4-6; film 1321070 item 4, Volume 3.)
- Chapman, Charles E. A History of California: The Spanish Period. New York, New York: Macmillan, 1921. (Family History Library fiche 6051216.)
- Hunt, Rockwell Dennis. California and Californians. Four Volumes. Chicago, Illinois: Lewis Publishing Company, 1932. (Family History Library book 979.4 H2h; film 1000092 items 1-4.)
- Schlesinger, Jr., Arthur M. The Almanac of American History. Greenwich, Conn.: Bison Books, 1983. (FHL book 973 H2alm)
- Dictionary of American History, Revised ed., 8 vols. New York: Charles Scribner's Sons, 1976. (FHL book 973 H2ad.)
- Webster's Guide to American History: A Chronological, Geographical, and Biographical Survey and Compendium. Springfield, Mass.: G&C Merriam, 1971. (FHL book 973 H2v)
- Limited view at Google Books
- Writings on American History By American Historical Association, Library of Congress, United States National Historical Publications Commission, Published by KTO Press, 1921 FHL book 973 H23w