A Republican, he served as San Francisco's mayor from 1931 to 1944. Rossi was mayor when the Golden Gate Bridge and the San Francisco–Oakland Bay Bridge were built, and he presided over the building of Treasure Island and the Golden Gate International Exposition (World's Fair) of 1939. Under his administration, the city resisted compliance with the Raker Act which required San Francisco to sell power from the Hetch Hetchy Reservoir in Yosemite to municipalities or municipal water districts, and not to any corporations, a condition of use of the Hetch Hetchy Valley. He dedicated the Mount Davidson Cross in March, 1934. He was a strong proponent of the New Deal alphabet-soup roster of work programs and worked vigorously and constantly with Washington to bring as many dollars to the city as possible in order to create jobs and improve the city's infrastructure.
