Morrison Knudsen collection on Boise Depot restoration

The Boise Depot, originally named Union Pacific Railroad Depot, was built by Union Pacific Railroad beginning in 1924. In 1922 a contract between Oregon Short Line, a subsidiary of Union Pacific Railroad, and the Boise Chamber of Commerce agreed to build a railroad line to provide through train service by way of Boise. Union Pacific hired New York architects Carrere, Hastings, Shreve and Lando to prepare plans for a Spanish-style station. The construction contract was awarded to Cherdon Construction Co. of Salt Lake City, with construction beginning on August 1, 1924. L.W. Althoff oversaw construction as engineer in charge with Boise contractor John U. Rathman supervising interior decorating. An opening ceremony was held on April 16, 1925, attended by Idaho Governor C.C. Moore and Boise Mayor E.B. Sherman. In 1927 chimes were added to the clock tower by the friends of Edward Henry Harriman in his honor, and on August 21 of that same year the Howard Platt Gardens, designed by Ricardo Espino, were dedicated.

The building was placed on the National Register of Historic Places on August 7, 1974. Union Pacific completed renovations and repairs on the building throughout its ownership, but in 1987 announced plans to sell the branch line that connected Boise to their main line. Morrison Knudsen Corporation purchased the depot building on December 13, 1990, renaming it the Morrison Knudsen Depot. Union Pacific donated the Platt Gardens to the City of Boise which had been responsible for maintenance and management since 1982.

After purchasing the property, Morrison Knudsen awarded a contract for historic preservation and restoration plans to Boston architectural firm Notter, Finegold & Alexander Inc. Morrison Knudsen acted as the general contractor while awarding 99% of subcontract work to Ada County small businesses. The restoration work was based on the original 1924 plans that came with the building plus study of old records from the company archive of Union Pacific Railroad in Omaha, Nebraska—apart from the addition of an elevator and supplementary staircase in the clock tower to provide access to views of downtown Boise. The original Barkalow Brothers newsstand was also uncovered—due to decrease in passenger services it was walled over in 1962.

The building reopened to the public on February 5, 1993. In 1996 Morrison Knudsen sold the property to the City of Boise.