Acosta had an older brother, Roberto, born in 1934.
After the family moved to California, the children were raised in the small San Joaquin Valley rural community of Riverbank, near Modesto.
Acosta's father was drafted during World War II.
After finishing high school, Acosta joined the United States Air Force.
Following his discharge, he worked his way through Modesto Junior College.
Acosta went on to San Francisco State University where he studied creative writing, becoming the first member of his family to get a college education.
1935
Oscar "Zeta" Acosta Fierro (April 8, 1935 – disappeared 1974) was a Mexican American attorney, author and activist in the Chicano Movement.
1966
He attended night classes at San Francisco Law School and passed the state bar exam in 1966.
1967
In 1967, Acosta began working locally as an antipoverty attorney for the East Oakland Legal Aid Society.
In the summer of 1967, Acosta met author Hunter S. Thompson.
1968
In 1968, Acosta moved to East Los Angeles and joined the Chicano Movement as an activist attorney, defending Chicano groups and activists.
He represented the Chicano 13 of the East L.A. walkouts, members of the Brown Berets, Rodolfo Gonzales, and other residents of the East L.A. barrio.
Acosta's controversial defenses earned him the ire of the Los Angeles Police Department, who often followed and harassed him.
1970
In 1970, he ran for sheriff of Los Angeles County against Peter J. Pitchess, and received more than 100,000 votes.
During the campaign, Acosta was jailed for two days for contempt of court.
He vowed that if elected, he would do away with the Sheriff's Department as it was then constituted.
Known for loud ties and a flowered attaché case with a Chicano Power sticker, Acosta lost to Pitchess' 1.3 million votes but beat Everett Holladay, chief of police of Monterey Park.
1971
Thompson characterized him as a heavyweight Samoan attorney, Dr. Gonzo, in his 1971 novel Fear and Loathing in Las Vegas.
In 1971, Thompson wrote an article about Acosta and the injustice in the barrios of East Los Angeles, as well as the death of Salazar, for Rolling Stone magazine, titled "Strange Rumblings in Aztlan".
While working on that article, Thompson received an offer from Sports Illustrated to cover an off-road race outside Las Vegas.
He invited Acosta to join him, and the two men returned to Las Vegas for a second weekend.
Thompson wrote about their adventures in a two-part article for Rolling Stone that appeared in 1971.
The following year, Random House published Fear and Loathing in Las Vegas as a nonfiction title.
The legal department of the publisher of Fear and Loathing said the book could not be published without clearance by Acosta, as references to him were recognizable.
Acosta initially refused the clearance, saying that he was insulted by Thompson's alteration of his race—Thompson had described him as a "300-pound Samoan."
He understood, however, that inserting his real name and race would necessitate extensive rewriting and delay publication of the book, so he promised clearance provided that his name and picture would appear on the dustjacket.
He later claimed a portion of the film rights, which led to more acrimony.
Scholar David S. Wills, in High White Notes: The Rise and Fall of Gonzo Journalism, argued that it was Acosta who pushed Thompson to pursue the theme of the American Dream and indeed provided much of the plot of the novel through his actions in Las Vegas.
He asserts that this is likely the reason why Acosta felt so aggrieved, citing various letters and audio recordings of the two men.
Acosta even complained to one of Thompson's editors, "Hunter has stolen my soul. He has taken my best lines and has used me."
Although Thompson and Acosta attempted to work together one more time, their relationship was strained by the dispute over Fear and Loathing in Las Vegas, and it never fully recovered.
After Acosta's death, it took Thompson several years before he wrote an obituary for his friend, "The Banshee Screams for Buffalo Meat".
In it, Thompson called Acosta "a stupid, vicious quack with no morals at all and the soul of a hammerhead shark."
Ralph Steadman explained that Thompson "berated most of his friends a lot, but somehow it was funny. His way of expressing love for people was to be both angry and insulting."
1972
He wrote the semi-autobiographical novels Autobiography of a Brown Buffalo (1972) and The Revolt of the Cockroach People (1973), and was friends with American author Hunter S. Thompson.
In 1972, Acosta published his first novel, Autobiography of a Brown Buffalo, about a lawyer fighting for the rights of a marginalized people.
1973
In 1973, he published The Revolt of the Cockroach People, a fictionalized version of the 1970 Chicano Moratorium as well as an account of the death of Los Angeles Times columnist Rubén Salazar.
1974
Acosta disappeared in 1974 during a trip in Mexico and is presumed dead.
Oscar Acosta was born in El Paso, Texas, to Manuel and Juanita (née Fierro) Acosta, from Mexico and El Paso, respectively.
He was the third child born, but second to survive childhood.