Lebanon High School was originally built in the spring of 1909 across the street from the old Santiam Academy (established 1851), at a cost of $40,000, by Mr. McChesney of Albany, Oregon, contractor, and P.C.

Over the next few decades, the population of Lebanon grew and the attendance at the institution swelled to such a degree that it eventually became a high school solely serving grades 9-12.

In 1957, Lebanon Union High School was built at the 41-acre (170,000 m2), Fifth Street and Airport Road site where it is currently located.

Intended to deal with issues of insufficient quality facilities, asbestos, and the planned changes to the school's structure, this involved the demolition of several buildings, including the literature wing (which was rebuilt as the short-lived "Freshman Hall") and art wing, as well as the construction of a new gym, parking lot, and tennis courts.

For the 151 years, from 1851 when Santiam Academy was established to 2002 when LMS was demolished, the site of the original LHS stands as the longest continuously operating public education facility in state history.