Unser came from a family of racecar drivers. He won numerous racing championships throughout his career, including three Indianapolis 500 titles. He debuted in 1955 at Pike's Peak, dubbed "Unser's Peak" because of his family's history of success at the hill climb. He finished fifth that year, behind his two brothers. A year later he won his first of a record 13 championships at Pike's Peak. He won six straight titles from 1958 to 1963. His streak ended in 1964 when his younger brother Al won the race.