The following important events in the history of Delaware affected political jurisdictions, family movements, and record keeping.
- 1631: New Netherland Dutch build fort at Zwaanendael (Lewes, Sussex, Delaware).
- 1638: New Sweden Swedes and Finns begins settling in the Fort Christina (Wilmington, New Castle, Delaware) area.
- 1655: New Sweden was conquered by New Netherland.
- 1664: New Netherland including Delaware became a British colony as part of an Anglo-Dutch war.
- 1682-1776: Pennsylvania's governor assumes control of Delaware over the objections of Maryland's claims as far north as Philadelphia. Delaware had its own provincial assembly after 1703.
- 1684-1736: The colonial government of Maryland laid claim to southern and western Delaware.
- 1776: Delaware declared its independence from Britain and established a government separate from that of Pennsylvania.
- 1787: (December 7,) Delaware became the first state.
- 1861-1865: During the Civil War, Delaware was a Union state.
- 1898: Over 300,000 men were involved in the Spanish-American War which was fought mainly in Cuba and the Philippines.
- 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.
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. One of the best sources for studying Delaware history is:
- History of Delaware, 1609-1888.  An excellent, detailed history with names, dates, and places.
Scharf's book is indexed in: Index to History of Delaware, 1609-1888 
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 Delaware 's history use the Internet Google search for phases like "Delaware history." Family History Library Catalog Surname Search lists many more histories under topics like:
- DELAWARE - HISTORY
- DELAWARE. [COUNTY] - HISTORY
- DELAWARE, [COUNTY], [TOWN] - HISTORY
- DELAWARE, BIBLIOGRAPHY
- 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.)
- Scharf, John Thomas. History of Delaware, 1609-1888. Two volumes. Tucson, Arizona: W. C. Cox, 1974. (Family History Library film 1000154.)
- Coghlan, Gladys M. Index to History of Delaware, 1609-1888. Wilmington, Delaware: Historical Society of Delaware, 1976. (Family History Library book 975.1 H2s index; fiche 6088424-26.)
- 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