The Southern Pacific Railroad, arrived in Tucson in 1880 and replaced their first wooden depot with an interesting complex of buildings in 1907, including the depot plus the railway express, records vault and stationmaster buildings. The depot boasts an interesting archetectural history; originally sporting Spanish Colonial Revival architecture, SP modified and enlarged the building in 1941 with an Art Moderne update. Now it is a huge building, 400 foot long, with two massive towers in front (plus one trackside) with massive square corner columns and lesser columns along the front porch. It now appears as a modern, stream-lined and somewhat "plain" big building with a white, smooth stucco finish all-around. Other than the red tile roof, little of the Spanish character shows. The 3 accompanying buildings maintained their original Spanish Colonial character in the 1940's makeover, that would have included the smooth stucco walls (in a tan/beige color) along with arched window and door openings, and low-pitched red clay, tile roof with wide broad-eaved gable roof lines.
The city purchased the complex from UP in 1998 and restored it by 2004. It is on the National Register of Historic Places as a part of the Tucson Warehouse Historic District, which received its designation in 1999. The depot serves the Tucson Amtrack depot and has small private business enterprises. The Southern Arizona Historical Museum is housed in the Records Vault building (see Arizona attraction No. 56 ). SP Locomotive No. 1673 - a 2-6-0 M-4b Mogul steam locomotive, built in 1900, is on display. It was designated on the National Historic Register in 1992.