When the railroad opened, the station at Millbrae was known as the 17 Mile House, because of its distance from San Francisco, but it got the name “Millbrae” in 1865. The land where the first Millbrae depot was built was donated by banker and philanthropist Darius O. Mills, who wanted his friends to be able to visit him by train at his estate called Happy House.
Completed in 1864 as an adobe structure, the first Millbrae depot was used to ship milk from the Dairy Mill’s owned with his partner F.H. Green. Green also operated the first post office at the depot. After the first depot was destroyed in a fire, a wooden structure replaced it, but it too burned down, in 1906.
The third Millbrae depot was built in 1907. Railroad magnate E.H. Harriman controlled a number of railroads during this period, including the Southern Pacific, and his men standardized the design of everything from locomotives to track spikes to depots.
The Millbrae depot, with its semicircular bay window and cast iron columns, might be best termed Colonial Revival in style, with a colonnade supporting an arcade roof over the shelter platforms. The first story contained an office, waiting room and baggage room, while the second story contained about 700 square feet of living quarters for the station agent and his family.
In 1976, SP wanted to destroy the Millbrae depot to add more parking spaces but the newly formed Millbrae Historical Society saved it by having it declared a national historic landmark. The depot was moved about 200 feet to the south in 1980 to make room for the Millbrae Avenue overpass.
This Millbrae depot ceased to be used in rail service in 2003 when the new Millbrae Intermodal Terminal for BART and Caltrain opened, and Caltrain passenger service shifted north to the new facility. The depot had been used for Caltrain signal maintenance offices and a café until 2004, when the building was converted into the Millbrae Train Museum.