This Mission/Spanish Revival post offices was designed by Birge M. Clark who also designed several of the buildings in the Ramona Street Historic District. The following paragraphs are excerpted from the Birge Clark web page of the Palo Alto History Project.

Birge Clark’s father was an architect, Stanford Professor and mayor of Mayfield. A longtime friend of Herbert Hoover, Arthur Clark constructed the future president’s home in 1919 with assistance from young Birge....

He was also immensely talented. In his early days, Clark worked almost exclusively in the fairly short-lived, but locally popular architectural style, variously referred to as Spanish Colonial Revival, California Colonial or the closely-related, Mission Revival. Although there were variations, the style most often consisted of stucco wall, red clay roof tiles, cast concrete ornaments and wrought iron grilles. Popular between 1915 and 1931, this romantic fashion caught on in many places with a Spanish past --- Florida, Texas and especially California....

But while Spanish motifs may have been all the rage in 1920s California, things were a little different back East. Presenting his blueprints for Palo Alto’s post office to the nation’s postmaster general in Washington, Clark was ridiculed. As long-time employee and associate Joseph Ehrlich tells the story, “The postmaster pushed them away and said, ‘Don’t you know what a U.S. post office looks like? We expect a stately building with neo-Romanesque columns showing the power of the federal government. I cannot approve this design.’…Birge responded, ‘Ok, but I don’t think the President and First Lady are going to be pleased with the design change.’” After revealing that the Hoovers had already approved the plans while Clark was breakfasting with his old friends that morning, the postmaster had a sudden change of heart and approved every blueprint in front of him.