Horizon School was built in 1992 to serve the needs of a growing student population in the Boise District's western border area. Horizon and Riverside, located in east Boise, were built in the same year.

Horizon is located about two miles west of Boise's Towne Square Mall, alongside several businesses which have located on Emerald Street. Many of Horizon's original students formerly attended Cole, Maple Grove, and Jackson Schools, but much of the attendance area is a result of new growth and development.