Cassady was born to Maude Jean (Scheuer) and Neal Marshall Cassady in Salt Lake City, Utah. His mother died when he was ten, and he was raised by his alcoholic father in Denver, Colorado. Cassady spent much of his youth either living on the streets of skid row with his father or in reform school.  As a youth, Cassady was repeatedly involved in petty crime. He was arrested for car theft when he was 14, for shoplifting and car theft when he was 15, and for car theft and fencing when he was 16.

In 1941, the 15-year old Cassady met Justin W. Brierly, a prominent Denver educator. Brierly was well known as a mentor of promising young men and was impressed by Cassady’s intelligence. Over the next few years, Brierly took an active role in Cassady’s life. Brierly helped admit Cassady to East High School where he taught Cassady as a student, encouraged and supervised his reading, and found employment for him. Cassady continued his criminal activities, however, and was repeatedly arrested from 1942 to 1944; on at least one of these occasions, he was released by law enforcement into Brierly’s safekeeping. In June of 1944, Cassady was arrested for possession of stolen goods, and served eleven months of a one-year prison sentence. He and Brierly actively exchanged letters during this period, even through Cassady’s intermittent incarcerations; this correspondence represents Cassady’s earliest surviving letters. Brierly, a closeted homosexual, is also believed to have been responsible for Cassady’s first homosexual experience.

In October 1945, after being released from prison, Cassady married the sixteen-year-old LuAnne Henderson. In 1946, Cassady and his wife traveled to New York City to visit their friend, Hal Chase, another protege of Brierly’s. It was while visiting Chase at Columbia University that Cassady met Jack Kerouac and Allen Ginsberg.[6] Although Cassady did not attend Columbia, he soon became friends with them and their acquaintances, some of whom later became members of the Beat Generation. While in New York, Cassady persuaded Kerouac to teach him to write fiction. Carolyn Cassady has stated that, “Neal, having been raised in the slums of Denver amongst the world’s lost men, [was] determined to make more of himself, to become somebody, to be worthy and respected. His genius mind absorbed every book he could find, whether literature, philosophy or science. Jack had had a formal education, which Neal envied, but intellectually he was more than a match for Jack, and they enjoyed long discussions on every subject.”

Carolyn Robinson met Cassady in 1946 while she worked in Denver, Colorado as a teaching assistant. Carolyn would leave the Beat group shortly after walking in on Neal, Allen Ginsberg, and Neal’s wife, LuAnne, in bed together. Five weeks after her departure, Neal got an annulment from LuAnne and married Carolyn on April 1, 1948. Carolyn Cassady’s book, Off the Road, details her marriage to Cassady and recalls him as, “the archetype of the American Man.”  During this period, Cassady worked for the Southern Pacific Railroad and kept in touch with his “beat” acquaintances, even as they became increasingly different philosophically.

The couple eventually had three children and settled down in a ranch house in Monte Sereno, California, 50 miles south of San Francisco, where Kerouac and Ginsberg sometimes visited. This home, built in 1954 with money from a settlement from Southern Pacific Railroad for a train related accident, was demolished in August of 1997. In 1950, Cassady entered into a bigamous marriage with Diane Hansen, a young model who was pregnant with his child, and he fathered one son, Curtis Hansen.  It has also been reported that Cassady had a sexual relationship with Ginsberg, which lasted off and on for the next twenty years.  Cassady traveled cross-country with both Kerouac and Ginsberg on multiple occasions, including the trip that is documented in Kerouac’s On the Road.

Following an arrest in 1958 for offering to share a small amount of marijuana with an undercover agent at a San Francisco nightclub, Cassady served a two-year sentence at California’s San Quentin State Prison in Marin County. After his release in June 1960, he struggled to meet family obligations, and Carolyn divorced him when his parole period expired in 1963. Carolyn stated that she was looking to remove the burden of supporting a family from Cassady, but “this was a mistake and removed the last pillar of his self-esteem.”  After the divorce, Cassady shared an apartment with Allen Ginsberg and Beat poet Charles Plymell in 1963 at 1403 Gough Street, San Francisco.

Cassady first met author Ken Kesey during the summer of 1962; he eventually became one of the Merry Pranksters, a group who formed around Kesey in 1964 who were vocal proponents of the use of psychedelic drugs. During 1964, Cassady served as the main driver of the bus named “Furthur” on the iconic first half of the journey from San Francisco to New York, which was immortalized by Tom Wolfe’s book, The Electric Kool-Aid Acid Test. Cassady appears at length in a documentary film about the Merry Pranksters and their cross-country trip, Magic Trip, directed by Alex Gibney, released on 5 August 2011.

In January 1967, Cassady traveled to Mexico with fellow prankster George “Barely Visible” Walker and Cassady’s longtime girlfriend Anne Murphy. In a beachside house just south of Puerto Vallarta, Jalisco, they were joined by Barbara Wilson and Walter Cox. All-night storytelling, speed drives in Walker’s Lotus Elan, and the use of LSD made for a classic Cassady performance — “like a trained bear,” Carolyn Cassady once said. Cassady was beloved for his ability to inspire others to love life. Yet, at rare times, he was known to express regret over his wild life, especially as it affected his family. At one point, Cassady took Cox, then 19, aside and told him, “Twenty years of fast living — there’s just not much left, and my kids are all screwed up. Don’t do what I have done.”

During the next year, Cassady’s life became less stable and the pace of his travels became more frenetic. He left Mexico in May, traveling to San Francisco, Denver, New York City, and points in-between. Cassady then returned to Mexico in September and October (stopping in San Antonio, on the way to visit his oldest daughter who had just given birth to his first grandchild), visited Ken Kesey’s Oregon farm in December, and spent the New Year with Carolyn at a friend’s house near San Francisco. Finally, in late January 1968, Cassady returned to Mexico once again.

On February 3, 1968, Cassady attended a wedding party in San Miguel de Allende, Guanajuato, Mexico. After the party, he went walking along a railroad track to reach the next town, but passed out in the cold and rainy night wearing nothing but a T-shirt and jeans. In the morning, he was found in a coma by the tracks, reportedly by Dr. Anton Black, later a professor at El Paso Community College, who carried Cassady over his shoulders to the local post office building. Cassady was then transported to the closest hospital where he died a few hours later on February 4, four days short of his forty-second birthday.

The exact cause of Cassady’s death remains uncertain. Those who attended the wedding party confirm that he took an unknown quantity of secobarbital, a powerful barbiturate sold under the brand name of Seconal. The physician who performed the autopsy wrote simply, “general congestion in all systems.” When interviewed later, the physician stated that he was unable to give an accurate report because Cassady was a foreigner and there were drugs involved. “Exposure” is commonly cited as his cause of death, although his widow believes he may have died of renal failure.