Ian Ernest Gilmore Green (or Gilmore Ian Rodrigo Green) was born May 13, 1912, in Toronto, Canada, the son of Margaret Julia MacChonechy and a father he never knew. He took the name of his stepfather, and thus became Gil Evans. His stepfather was a miner, whereas his mother took care of the children of rich families, and prepared meals for campsites. Moving wherever work would take them, they went from one North-American mining site to the next, including Saskatchewan, British Columbia, and such Northwestern U.S. states as Idaho, Montana, and Washington. Their child was put in boarding houses, moving from one family to the next, until they finally settled permanently in California, around 1922. Gil went to school in Berkeley, and there, his real musical training began. The father of one of his friends was a jazz fanatic and initiated him to this music. In 1927, he took the two teenagers to see Duke Ellington at the Orpheum theater in San Francisco.
It was a revelation for Gil Evans, who decided to devote his life to this music. That same year, he bought his first record, No One Else But You, by Louis Armstrong and Earl Hines. At the same time, he started transcribing, from the recordings, the music of such great jazz arrangers as Red Nichols, Duke Ellington, and Don Redman. In 1933, he put together his first group in Stockton, which had six musicians at first, but grew to nine in 1934. The group played arrangements by Don Redman, Fletcher Henderson, and Duke Ellington, all transcribed from the recordings. In 1935, the orchestra was on the same bill at the Palomar Ballroom as the triumphant Benny Goodman, then was hired to play at the Rendez-Vous Ballroom in Balboa Beach, in southern California, where it remained until 1938. Gil Evans was in charge of writing and conducting, and, from time to time, Stan Kenton held the piano chair.