(Information taken directly from Wikipedia.)
Luke Cage first appeared in Luke Cage, Hero For Hire #1 (June, 1972).
Luke Cage was born by the name of Carl Lucas. Born and raised in New York City's Harlem neighborhood, Lucas spends his youth in a gang called the Rivals. With his friend Willis Stryker, he fights the rival gang the Diablos and commits petty thefts, often on behalf of deformed crime lord Sonny Caputo, a.k.a. Hammer. In and out of juvenile homes throughout his teens, Lucas dreams of becoming a major New York racketeer until he finally realizes how his actions are hurting his family. He seeks to better himself as an adult by finding legitimate employment. Meanwhile, Stryker rises through the ranks of crime, but the two men remain friends. When Stryker's activities anger the Maggia (a.k.a. the Syndicate), he is badly beaten in a mob hit, saved only by Lucas' intervention. When Stryker's girlfriend, Reva Connors, breaks up with him in fear of his violent work, she seeks solace with Lucas. Stryker is convinced that Lucas is responsible for the breakup, so he plants heroin in Lucas' apartment and tips off the police. Lucas is arrested and sent to prison where contact with his family is sparse due to the resentment of his brother James, Jr., who intercepts Lucas' letters to their father James and eventually leads each to believe the other is dead.
In prison, Lucas is consumed by rage over Stryker's betrayal and his father's supposed death, engaging in frequent brawls and escape attempts. Eventually transferred to Seagate Prison off the coast of Georgia, he becomes the favorite target of sadistic guard Albert "Billy Bob" Rackham, whose brutality ultimately leads to a demotion that he blames on Lucas. Later, research scientist Dr. Noah Burstein recruits Lucas as a volunteer for experimental cell regeneration based on a variant of the Super-Soldier process he had previously used to empower Warhawk. Burstein immerses Lucas in an electrical field conducted by an organic chemical compound; when he leaves Lucas unattended, Rackham alters the experiment's controls, hoping to maim or kill Lucas. Lucas' treatment is accelerated past its intended limits, inducing body-wide enhancements that give him superhuman strength and durability. He uses his new power to escape Seagate and makes his way back to New York, where a chance encounter with criminals inspires him to use his new powers for profit.
Adopting the alias Luke Cage and donning a distinctive costume, he launches a career as a Hero for Hire, helping anyone who can meet his price. He soon establishes an office above Times Square's Gem Theater, where he befriends film student D. W. Griffith. Burstein, aware of his friend's innocence, also relocates to New York and opens a medical clinic, assisted by Dr. Claire Temple, whom Cage begins dating. Although Cage is content to battle strictly conventional criminals, he soon learns that New York is hardly the place to do so. Stryker himself has become a Maggia agent known as Diamondback and dies battling Cage. Subsequent opponents included Gideon Mace, an embittered veteran seeking a U.S. takeover; Chemistro (Curtis Carr), whose Alchemy Gun is a weapon later used by others, including his own brother after Curtis reformed; and Discus, Stiletto, Shades, and Commanche, all criminals with ties to Cage's prison days who face him repeatedly over the years.