The building served as the headquarters for the
Southern Pacific Railroad after it relocated from the
Flood Building in 1917, ten years after SP had moved into the Flood Building. At its completion, the building's first floor was devoted to retail except for the portion facing the rear courtyard (opening to Mission Street), which was reserved for Southern Pacific. It was later incorporated into the 1976 One Market Plaza development which includes Spear Tower and Steuart Tower. However, Union Pacific Railroad was still the owner of One Market Street until the building was sold for to The Martin Group (TMG) in 1998. TMG invested another $50 million to renovate the property, Equity Office Properties Trust sold One Market Street to The Blackstone Group in February 2007, and Blackstone, in turn, sold One Market to Morgan Stanley in June 2007 as part of a large real estate acquisition. Morgan Stanley sold approximately half of One Market Plaza to The Paramount Group in July 2007. One Market Plaza was owned jointly by
Morgan Stanley (49% share) and The Paramount Group (51% share) until Morgan Stanley sold its share to
Blackstone Real Estate Partners in 2014 for . ==Design==