Wyatt Berry Stapp Earp was born on March 19, 1848, in Monmouth, Illinois. His father, Nicolas Porter Earp, was a wounded veteran of the Mexican War and a farmer and harness maker. On occasion he also served as justice of the peace. Wyatt's mother was Virginia Cooksey. In 1850 the family moved to Pella, Iowa. When the civil war broke out, Wyatt's two older brothers, James and Virgil, along with their half brother, Newton, joined the Union Army. James was severely wounded and spent seventeen months in the hospital recovering. Wyatt attempted to enlist but his father prevented it. In 1863 the family moved to San Bernardino County, California, where Nicolas established a small farm. After the civil war, when Virgil rejoined the family, he and Wyatt took jobs as teamsters on freight wagons operating between Southern California and Salt Lake City. In 1868, Nicolas moved the family back to Iowa.
Apparently Wyatt did not like the life of a farmer and soon moved to Lamar, Missouri, where he was hired as a constable on March 3, 1870. In May he married Urilla Southerland. In November, Wyatt was elected to the post of constable. Early in 1871 Urilla died suddenly. The cause of her death is not known. Some say she died in childbirth, others say typhoid fever. Immediately after her death, Wyatt and his brothers engaged in a street fight with Urilla's two brothers. The origin of the fight is unknown, but several months later Wyatt left town under a cloud of suspicion that he had defrauded a neighbor out of twenty dollars. From Lamar he went to the Indian Territory (Oklahoma) where he was engaged in an incident which raised the possibility that he stole another man's horse. Earp went on to be a professional hunter for a government survey crew. In 1871 he hunted buffalo and it was during this period that he got to know Ed and Bat Masterson. In June 1873, Wyatt appears to have played an important role in disarming and arresting a famous gunman, Ben Thompson in Ellsworth, Kansas. The exact events are unclear at this point, but bystanders at the time were impressed and Wyatt's reputation as a cool hand under pressure was off to a good start.
In 1874 Wyatt served unofficially as deputy town marshall under Marshall Bill Smith in Wichita, Kansas. He was officially appointed to the position by newly elected Marshall Mike Meagher on April 21, 1875. Texas ranchers were just beginning to drive their cattle to the new railhead in Wichita. Life after dark was lively in town as the drovers spent their earnings on whiskey, women and gambling. The task of the constabulary was to maintain order, but not to do so in such a way as to discourage business. Wyatt handled his job well, but fell into disfavor with former Marshall Smith who was attempting to regain his position as town marshall. In 1876 Wyatt got into a fist fight with Smith and was arrested and fined for disorderly conduct. During the election, Wyatt and his brother Jim were criticized for being involved in prostitution. (Jim's wife was thought to be running a house of prostitution under the protection of the Earp brothers.) Meagher was reelected over Smith and wanted to keep Wyatt as a deputy. He was unable to convince the town council and Wyatt was taken off of the city payroll.
In April 1876, George Hoover was elected mayor of Dodge City. Dodge was divided between Hoover and his German immigrant farmer supporters and the "Dodge City Gang" led by James H. Kelley (nicknamed "Dog Kelley because he kept a pack of greyhound dogs). The Gang was composed primarily of saloon owners, gamblers, and brothel operators. Hoover appointed Larry Deger town marshall and sent for Wyatt Earp to be Deger's principal assistant and chief enforcer. Shortly after taking the assistant position Wyatt hired his brother Jim and Bat Masterson as deputies. In the fall of 1876, Wyatt and Morgan Earp went to Deadwood, but returned to Dodge in July 1877, shortly after Ed Masterson took the position of Deger's assistant and chief enforcer. Wyatt was not offered a job on the police force. He did do some bounty work and while chasing a bank robber in October 1877, in Fort Griffin, Texas, Wyatt first met Dr. John Henry Holiday and his common law wife, Mary Katherine Harony (also known as "Big Nose Kate"). The two men hit it off well and became friends.