The local community received its first post office in April 1907 under the name Diaz, but because another Texas town had already been awarded that name by postal officials, the post office was renamed San Benito later that year. Colonel Samuel A. Robertson served as the first postmaster, and Emma (Purvis) Agar became the first of several women postal clerks to serve in San Benito. Municipal delivery began in 1925 along two routes. The post office operated from several locations in San Benito until moving in 1933 to a newly constructed Federal office building on park land donated by the city. It opened on April 16, 1933, one day after an estimated 3,000 people attended an open house to inspect the building. At its opening, the Federal building also housed offices of the International Boundary Commission, the U.S. Departments of Agriculture and Immigration, and the U.S. Civil Service Commission. The post office also served as a social gathering place for many people in the community and currently serves San Benito and the surrounding towns of Los Indios, Blue Town, Arroyo City, Lozano, Las Yescas, Laurles, La Paloma, El Ranchito, and Rio Hondo.