The SCA's roots can be traced to a backyard party of a UC Berkeley medieval studies graduate, the author Diana Paxson, in Berkeley, California, on May Day in 1966. The party began with a "Grand Tournament" in which the participants wore helmets, fencing masks, and usually some semblance of a costume, and sparred with each other using weapons such as plywood swords, padded maces, and fencing foils. It ended with a parade down Telegraph Avenue with everyone singing "Greensleeves". The SCA still measures dates within the society from the date of that party, calling the system Anno Societatis (Latin for "in the Year of the Society"). For example, 2009 May 1 to 2010 April 30 was A.S. XLIV (44). The name Berkeley Society for Creative Anachronism was coined by science fiction author Marion Zimmer Bradley, an early participant, when the nascent group needed an official name in order to reserve a park for a tournament. "Berkeley" was dropped as the group expanded. Three other co-founders were science fiction author Poul Anderson, his wife, writer Karen Kruse Anderson, and their daughter, Astrid.

In 1968, Bradley and her husband Walter Breen moved to Staten Island, New York where they co-founded the Kingdom of the East, holding a tournament that summer to determine the first Eastern King of the SCA. That September, a tournament was held at the 26th World Science Fiction Convention, which was in Berkeley that year. The SCA had produced a book for the convention called A Handbook for the Current Middle Ages, which was a how-to book for people wanting to start their own SCA chapters. Convention goers purchased the book and the idea spread. Soon, other local chapters began to form. In October 1968, the SCA was incorporated as a 501(c)(3) non-profit corporation in California. By the end of 1969, the SCA's three original kingdoms had been established: West Kingdom, East, and Middle. All SCA kingdoms trace their roots to these original three. The number of SCA kingdoms has continued to grow by the expansion and division of existing kingdoms; for example, the kingdoms now called the Outlands, Artemisia, Ansteorra, Gleann Abhann, Meridies, and Trimaris all are made up of lands originally belonging to the fourth kingdom, Atenveldt, which began as a branch of the West Kingdom.

The SCA produces two quarterly publications, The Compleat Anachronist and Tournaments Illuminated, and each kingdom publishes a monthly newsletter.

The Compleat Anachronist is a quarterly monographic series, each issue focused on a specific topic related to the period of circa 600–1600 in history. Issues are written by SCA members and have covered a wide range of topics.

Tournaments Illuminated is a quarterly magazine, each issue covering a range of topics and including several features such as news, a humor column, book reviews, war reports and various articles on SCA-related topics of interest.

The SCA is incorporated as a 501(c)(3) non-profit corporation in California, with its current headquarters in the city of Milpitas, California. It is headed by a board of directors, each of whom is nominated by the membership of the SCA, selected by sitting directors, and elected to serve for 3.5 years. Each director serves as an ombudsman for various kingdoms and society officers. The BoD, as it is called, is responsible for handling the corporate affairs of the SCA and is also in charge of certain disciplinary actions, such as revoking the membership status of participants who have broken Corpora regulations or modern law while participating in SCA activities. Because the SCA now has groups all over the world, it has also been incorporated in other countries, e.g. SCAA in Australia, SCANZ in New Zealand, SKA Nordmark in Sweden, SKA in Finland, and the UK CIC which covers both the UK and Ireland. These affiliated bodies work with the U.S. BoD with regards to Societal issues, but make all decisions affected by local law independently of the U.S. parent body. Although they agree to work in unity with the U.S. SCA board of directors, they are autonomous and are not bound by any ruling of the U.S. body.
The SCA is divided into administrative regions that it calls kingdoms. Smaller branches within those kingdoms include Principalities, Regions, Baronies, and Provinces; and local chapters are known as Cantons, Ridings, Shires, Colleges, Strongholds, and Ports. Kingdoms, principalities, and baronies have ceremonial rulers who preside over activities and issue awards to individuals and groups. Colleges, strongholds, and ports are local chapters (like a shire) that are associated with an institution, such as a school, military base, or even a military ship at sea.

All SCA branches are organized in descending order as follows:
• Kingdom: Area ruled by a King and Queen (typically covering several U.S. states or Canadian provinces, and can be as large as countries or collections of countries). Minimum members required 400.
Groups are active all over the United States, Canada, Europe, Australia, Japan, South Africa, and New Zealand, with scattered groups elsewhere, including China, Israel, Panama and Thailand. At one time there was even a group on the aircraft carrier USS Nimitz, known as the "Shire of Curragh Mor" (anglicized Irish for "Big Boat"), and the shire's arms played on the Nimitz's ship's badge. There is also an active chapter in South Korea, the Stronghold of Warrior's Gate, with a mix of active duty military personnel from the several services and military-connected civilians. There are also non-territorial groups, usually called "households", which are not part of the Society's formal organization, the largest of which is the Mongol Empire-themed Great Dark Horde.
The twenty SCA Kingdoms and the geographic areas they co…

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