* Literature: Many historical plays are based on literary works, such as novels, poems, and biographies. For example, Shakespeare's "Romeo and Juliet" is based on a poem by Arthur Brooke, and his "Julius Caesar" is based on a biography by Plutarch.
* History books: Historical plays can also be based on history books and other historical documents. For example, the play "1776" is based on the book of the same name by David McCullough, and the musical "Hamilton" is based on the biography of Alexander Hamilton by Ron Chernow.
* Oral traditions: Some historical plays are based on oral traditions, such as myths and legends. For example, the play "Oedipus Rex" is based on a Greek myth, and the play "Joan of Arc" is based on a French legend.
* Personal experiences: Some historical plays are based on the author's personal experiences. For example, the play "The Glass Menagerie" is based on Tennessee Williams's experiences growing up in the South during the Great Depression.
* Imagination: Historical plays can also be based on the author's imagination. For example, the play "Amadeus" is based on a fictionalized account of the life of Wolfgang Amadeus Mozart.
No matter what their source, historical plays can provide a valuable way to learn about the past and to gain a greater understanding of the human condition.