James Butler Hickok was born May 27, 1837, in Homer, Illinois (present-day Troy Grove, Illinois) to william Alonzo Hickok, a farmer and abolitionist, and his wife Polly Butler. His father was said to have used the family house, now demolished, as a station on the Underground Railroad. He was the fourth of six children. william Hickok died in 1852, when James was 15. Hickok was a good shot from a young age and was recognized locally as an outstanding marksman with a pistol. Photographs of Hickok appear to depict dark hair, but all contemporaneous descriptions affirm that it was red.

Hickok's favorite guns were a pair of Colt 1851 Navy Model (.36 caliber) cap-and-ball revolvers. They had ivory grips and nickel plating and were ornately engraved with "J.B. Hickok–1869" on the backstrap. He wore his revolvers butt-forward in a belt or sash (when wearing city clothes or buckskins, respectively), and seldom used holsters per se; he drew the pistols using a "reverse", "twist" or cavalry draw, as would a cavalryman.

In 1855, at age 18, James Hickok fled Illinois following a fight with Charles Hudson, during which both fell into a canal (each thought, mistakenly, that he had killed the other). Hickok moved to Leavenworth in the Kansas Territory, where he joined "General" Jim Lane's Free State Army (also known as the Jayhawkers), a vigilante group active in the new territory. While a Jayhawker, he met 12-year-old william Cody (later known as Buffalo Bill), who despite his youth served as a scout just two years later for the U.S. Army during the Utah War.

In 1857, Hickok claimed a 160-acre (65-ha) tract in Johnson County, Kansas (near present-day Lenexa). On March 22, 1858, he was elected one of the first four constables of Monticello Township. In 1859, he joined the Russell, Waddell & Majors freight company, the parent company of the Pony Express.

In 1860, he was badly injured by a bear while driving a freight team from Independence, Missouri to Santa Fe, New Mexico. According to Hickok's account, he found the road blocked by a cinnamon bear and its two cubs. Dismounting, he approached the bear and fired a shot into its head, but the bullet ricocheted off its skull, infuriating it. The bear attacked, crushing Hickok with its body. Hickok managed to fire another shot, wounding the bear's paw. The bear then grabbed his arm in its mouth, but Hickok was able to grab his knife and slash its throat, killing it.

After the Civil War broke out in April 1861, James Hickok became a teamster for the Union Army in Sedalia, Missouri. By the end of 1861, he was a wagonmaster, but in September 1862 he was discharged for unknown reasons. He then joined General James Henry Lane's Kansas Brigade and, while serving with the brigade, saw his friend Buffalo Bill Cody, who was serving as a scout. There are no records of Hickok's whereabouts for the next year, although at least one source claims that he was a Union spy in Confederate territory during this time.

In late 1863 he worked for the provost marshal of southwest Missouri as a member of the Springfield detective police. His work included identifying and counting the number of troops in uniform who were drinking while on duty, verifying hotel liquor licenses, and tracking down individuals who owed money to the cash-strapped Union Army.

In 1864, Hickok had not been paid for some time and was hired as a scout by General John B. Sanborn. In June 1865, Hickok mustered out and went to Springfield, where he gambled. The 1883 History of Greene County, Missouri described him as "by nature a ruffian... a drunken, swaggering fellow, who delighted when 'on a spree' to frighten nervous men and timid women."

In 1865, Hickok recruited six Indians to accompany him to Niagara Falls, where he put on an outdoor demonstration called The Daring Buffalo Chasers of the Plains. Since the event was outdoors, he could not compel people to pay, and the venture was a financial failure.

Later that year, he moved to Kansas, where he ran for sheriff in Ellsworth County on November 5, 1867. He was defeated by a former soldier, E.W. Kingsbury.

On September 1, Hickok was in Lincoln County, Kansas, where he was hired as a scout by the 10th Cavalry Regiment, a segregated African-American unit. On September 4, Hickok was wounded in the foot while rescuing several cattlemen in the Bijou Creek Basin who had been surrounded by Indians. The 10th Regiment arrived at Fort Lyon in Colorado in October and remained there for the rest of 1868.

In September 1869, his first month as sheriff, Hickok killed two men. The first was Bill Mulvey, who was rampaging through town, drunk, shooting out mirrors and whisky bottles behind bars. Citizens warned Mulvey to behave, because Hickok was sheriff. Mulvey angrily declared that he had come to town to kill Hickok. When he saw Hickok, he leveled his cocked rifle at him. Hickok waved his hand past Mulvey at some onlookers and yelled, "Don't shoot him in the back; he is drunk." Mulvey wheeled his horse around to face those who might shoot him from behind, and before he realized he had been fooled, Hickok shot him through the temple.

On July 17, 1870, Hickok was attacked by two troopers from the 7th U.S. Cavalry, Jeremiah Lonergan and John Kyle (sometimes spelled Kile), in a saloon. Lonergan pinned Hickok to the ground, and Kyle put his gun to Hickok's ear. When Kyle's weapon misfired, Hickok shot Lonergan, wounding him in the knee, and shot Kyle twice, killing him. Hickok was not re-elected to office.

On October 5, 1871, Hickok was standing off a crowd during a street brawl when Coe fired two shots. Hickok ordered him to be arrested for firing a pistol within the city limits. Coe claimed that he was shooting at a stray dog, and then suddenly turned his gun on Hickok, who fired first and killed Coe. Hickok caught a glimpse of someone running toward him and quickly fired two more shots in reaction, accidentally shooting and killing Abilene Special Deputy Marshal Mike Williams, who was coming to his aid. This event haunted Hickok for the remainder of his life. There is another account of the Coe shootout: Theophilus Little, the mayor of Abilene and owner of the town's lumber yard, recorded his time in Abilene by writing in a notebook which was ultimately given to the Abilene Historical Society. Writing in 1911, he detailed his admiration of Hickok and included a paragraph on the shooting that differs considerably from the reported account:

McCall entered the saloon, walked up behind Hickok, drew his Colt's Model 1873 Single Action Army .45 caliber revolver and shouted, "Damn you! Take that!" He shot Hickok in the back of the head at point-blank range. Hickok died instantly. The bullet emerged through Hickok's right cheek and struck another player, riverboat Captain william Massie, in the left wrist. Hickok may have told his friend Charlie Utter and others who were traveling with them that he thought he would be killed while in Deadwood.

On August 1, 1876, Hickok was playing poker at Nuttal & Mann's Saloon in Deadwood, Dakota Territory. When a seat opened up at the table, a drunk man named Jack McCall sat down to play. McCall lost heavily. Hickok encouraged McCall to quit the game until he could cover his losses and offered to give him money for breakfast. Though McCall accepted the money, he was apparently insulted. The next day, Hickok was playing poker again. He usually sat with his back to a wall so he could see the entrance, but the only seat available when he joined the game was a chair facing away from the door. He twice asked another man at the table, Charles Rich, to change seats with him, but Rich refused.

Jack McCall was hanged on March 1, 1877, and buried in a Roman Catholic cemetery. The cemetery was moved in 1881, and when his body was exhumed, the noose was found still around his neck.

Hickok is known to have fatally shot six men and is suspected of having killed a seventh (McCanles). Despite his reputation, Hickok was buried in the Ingelside Cemetery, Deadwood's original graveyard. This cemetery filled quickly, and in 1879, on the third anniversary of his original burial, Utter paid to move Hickok's remains to the new Mount Moriah Cemetery. Utter supervised the move and noted that, while perfectly preserved, Hickok had been imperfectly embalmed. As a result, calcium carbonate from the surrounding soil had replaced the flesh, leading to petrifaction. One of the workers, Joseph McLintock, wrote a detailed description of the re-interment. McLintock used a cane to tap the body, face, and head, finding no soft tissue anywhere. He noted that the sound was similar to tapping a brick wall, and believed the remains to weigh more than 400 lb (180 kg). william Austin, the cemetery caretaker, estimated 500 lb (230 kg), which made it difficult for the men to carry the remains to the new site. The original wooden grave marker was moved to the new site, but by 1891 it had been destroyed by souvenir Hunters whittling pieces from it, and it was replaced with a statue. This, in turn, was destroyed by souvenir Hunters and replaced in 1902 by a life-sized sandstone sculpture of Hickok. This, too, was badly defaced, and was then enclosed in a cage for protection. The enclosure was cut open by souvenir Hunters in the 1950s, and the statue was removed.

The 1923 Western silent film movie Wild Bill Hickok was directed by Clifford Smith and starred william S. Hart as Hickok. The film was released on November 18, 1923, by Paramount Pictures. A print of the film is maintained in the Museum of Modern Art film archive.

The 1936 movie The Plainsman starring Gary Cooper as Wild Bill Hickok has the relationship with Buffalo Bill and Calamity Jane as its main plot line. It is a loose adaptation of J. B. Hickok's life ending with his infamous aces and eights card hand.

In 1979, Hickok was inducted into the Poker Hall of Fame.

A highly fictional account of Hickok's later years and death, titled Wild Bill, was released on December 18, 1995. The film starred Jeff Bridges as James Butler "Wild Bill" Hickok, David Arquette as Jack McCall and was written and directed by Walter Hill. Receiving mixed reviews, the film currently holds a 5.9 rating on the Internet Movie Database and a 41% rating on Rotten Tomatoes.

HBO, the premium cable network, produced and released the dramatic television series titled Deadwood, from 2004 to 2006. In episodes 1-4, Hickok is shown arriving in Deadwood with Charlie Utter and Calamity Jane, with the Deadwood camp inhabitants aware of Hickok's Celebrity status as a gunfighter and lawman. The series shows Hickok as an unsatisfied gambler who is eventually murdered while playing poker and subsequently laid to rest in Deadwood's cemetery.

At the time of his death Hickok was wearing a Smith & Wesson Model 2 Army Revolver, a newly released five-shot, single-action 38 cal. weapon. Bonhams auction company offered this pistol at auction on November 18, 2013, in San Francisco, California, described as Hickok's Smith & Wesson No. 2, serial number 29963, a .32 rimfire with a six-inch barrel, blued finish and varnished rosewood grips. The gun did not sell because the highest bid of $220,000 was less than the reserve set by the gun's owners.

Shortly before Hickok's death, he wrote a letter to his new wife, which read in part, "Agnes Darling, if such should be we never meet again, while firing my last shot, I will gently breathe the name of my wife—Agnes—and with wishes even for my enemies I will make the plunge and try to swim to the other shore."

A semi-fictionalized version of Hickok's time as Marshal of Abilene Kansas, titled Hickok was released on July 7, 2017. The film starred Luke Hemsworth as James Butler "Wild Bill" Hickok, Trace Adkins as Bulls Head saloonkeeper Phil Coe, Kris Kristofferson as Abilene mayor George Knox, and Kaiwi Lyman-Mersereau as John Wesley Hardin. It was written by Michael Lanahan and directed by Timothy Woodward Jr.

Hickok is currently interred in a ten-foot (3 m) square plot at the Mount Moriah Cemetery, surrounded by a cast-iron fence, with a U.S. flag flying nearby. A monument has been built there. It has been reported that Calamity Jane was buried next to him, according to her dying wish. Four of the men on the self-appointed committee who planned Calamity's funeral (Albert Malter, Frank Ankeney, Jim Carson, and Anson Higby) later stated that, since Hickok had "absolutely no use" for Jane in this life, they decided to play a posthumous joke on him by laying her to rest by his side. Potato Creek Johnny, a local Deadwood Celebrity from the late 19th and early 20th centuries, is also buried next to Wild Bill.