[4] The UCSB Gauchos and Cal Poly Mustangs met in their first collegiate athletic event on November 5, 1921.
[5][6][7] The rivalry heated up when both schools were members of the California Collegiate Athletic Association.
The two would remain in-conference rival until the Gauchos departed in 1969 for the newly formed Pacific Coast Athletic Association.
The two schools announced the formalization of the Blue–Green Rivalry in 2009 to highlight the athletic accomplishments, but also to promote environmental sustainability.
With both schools located on the Central Coast of California less than 100 miles apart, attendance has risen dramatically following the Gauchos' 2006 NCAA Division I Men's Soccer Championship.