The San Juan High School District was formed in 1913 and named after the original San Juan Spanish Land Grant. It served all students in the northern half of Sacramento County. Its first class met in a temporary two-story elementary school building located south of Winding Way and Dewey Drive. A new high school was built in 1915 on Greenback Lane east of Sylvan Road on land donated by Walter Trainor, an early real estate developer. Construction of San Juan High School was financed through a school bond of $3,500, and 50 students attended when the school opened.