Robert Emmet (4 March 1778 – 20 September 1803) was an Irish nationalist, Republican, orator and rebel leader. He led an abortive rebellion against British rule in 1803 and was captured, tried and executed for high treason. There's a goodly amount about him on Wikpedia if you want to read more.
His statue, which stands outside the California Academy of Sciences in Golden Gate Park, was donated to the city in 1919. The donation was made by by James D. Phelan, a former San Francisco mayor. Phelan, the son of an Irish immigrant, was a strong supporter of the Irish cause. The sculptor was Jerome Connor; three other examples are in Washington, DC; Dublin, Ireland; and Emmetsburg, Iowa.