He was a writer and major voice of the Beat Generation, a group of writers who gained prominence in the late 50s and early 60s. They emphasized free expression and experimentation in sex, drugs and behavior, and inspired others to do the same. They preceded and inspired the hippie lifestyle of the 60s.
Kerouac's novel On The Road became a major literary landmark of the Beat Generation. It was mostly an autobiographical collection of Kerouac's experiences on his road trips across the country.
