The American frontier comprises the geography, history, folklore, and cultural expression of life in the forward wave of American westward expansion since the colonial era. Enormous popular attention in the media focuses on the second half of the 19th century, a period sometimes called the Old West, or the Wild West. As defined by Hine and Faragher, "frontier history tells the story of the creation and defense of communities, the use of the land, the development of markets, and the formation of states." They explain, "It is a tale of conquest, but also one of survival, persistence, and the merging of peoples and cultures that gave birth and continuing life to America." Through treaties with foreign nations and native peoples, political compromise, technological innovation, military conquest, establishment of law and order, and the great migrations of foreigners, the United States expanded from coast to coast (Atlantic Ocean to Pacific Ocean), fulfilling advocates' belief in Manifest Destiny. In securing and managing the West, the U.S. federal government greatly expanded its powers, as the nation evolved from an agrarian society to an industrialized nation. First promoting settlement and exploitation of the land, by the end of the 19th century the federal government assumed stewardship of the remaining open spaces. As the American frontier passed into history, the myths of the west took firm hold in the imagination of Americans and foreigners alike.

Wyatt Berry Stapp Earp (March 19, 1848 – January 13, 1929) was an American investor and law enforcement officer who served in several Western frontier towns. He was also at different times a farmer, teamster, bouncer, saloon-keeper, miner and boxing referee. He is best known for his part in the Gunfight at the O.K. Corral during which three outlaw Cowboys were killed. The 30-second gunfight defined the rest of his life. Earp's modern-day reputation is that of the Old West's "toughest and deadliest gunman of his day."

Earp spent his early life in Iowa. His first wife Urilla Sutherland Earp died while pregnant less than a year after they married. Within the next two years he was arrested, sued twice, escaped from jail, then was arrested three more times for "keeping and being found in a house of ill-fame". He landed in the cattle boomtown of Wichita, Kansas where he became a deputy marshal for one year and developed a solid reputation as a lawman. In 1876 he followed his brother James to Dodge City, Kansas where he became an assistant marshal. In the winter of 1878 he went to Texas to gamble where he met John Henry "Doc" Holliday whom Earp credited with saving his life.

William H. Bonney (born William Henry McCarty, Jr.) est. November 23, 1859 – c. July 14, 1881, better known as Billy the Kid but also known as Henry Antrim, was a 19th-century American gunman who participated in the Lincoln County War and became a frontier outlaw in the West. According to legend, he killed 21 men, but he is generally accepted to have killed between four and nine.

McCarty (or Bonney, the name he used at the height of his notoriety) was 5 feet 8 inches (173 cm) to 5 feet 9 inches (175 cm) tall with blue eyes, a smooth complexion, and prominent front teeth. He was said to be friendly and personable at times, and many recalled that he was as "lithe as a cat". Contemporaries described him as a "neat" dresser who favored an "unadorned Mexican sombrero". These qualities, along with his cunning and celebrated skill with firearms, contributed to his paradoxical image, as both a notorious outlaw and beloved folk hero.

Relatively unknown during most of his lifetime, Billy was catapulted into legend in 1881 when New Mexico's governor, Lew Wallace, placed a price on his head. In addition, the Las Vegas Gazette (Las Vegas, New Mexico) and the New York Sun carried stories about his exploits. Many other newspapers followed suit. After his death, several biographies were written that portrayed the Kid in varying lights.

William Frederick "Buffalo Bill" Cody (February 26, 1846 – January 10, 1917) was an American soldier, bison hunter and showman. He was born in the Iowa Territory (now the U.S. state of Iowa), in Le Claire but lived several years in Canada before his family moved to the Kansas Territory. Buffalo Bill received the Medal of Honor in 1872 for service to the US Army as a scout. One of the most colorful figures of the American Old West, Buffalo Bill became famous for the shows he organized with cowboy themes, which he toured in Great Britain and Europe as well as the United States.

William Frederick Cody ("Buffalo Bill") got his nickname after the American Civil War when he had a contract to supply Kansas Pacific Railroad workers with buffalo meat. Cody earned the nickname by killing 4,280 American bison (commonly known as buffalo) in eighteen months, (1867–1868).Bill Comstock also had the nickname. Cody and Comstock competed in a buffalo-shooting match over the exclusive right to use the name, which Cody won by killing 69 bison to Comstock's 48.