After graduating from Columbia, he served as private secretary to his father for two years. He then returned to Columbia and attended Columbia Law School, graduating in 1873. From 1873 to 1874 he was aide-de-camp to Governor John Adams Dix with the rank of colonel. He was elected to twelve terms as a member of the New York State Assembly, representing Putnam County, in 1874, 1876, 1877, 1878, 1879, 1889, 1890, 1891, 1893, 1894, 1895 and 1896. He was the Republican leader in 1890 and Speaker in 1895 and 1896. He was selected in 1903 to serve as Assistant Treasurer of the United States in charge of the Wall Street sub-treasury in the Administration of Theodore Roosevelt. His first choice, Robert Bacon, declined the position. He withdrew his second choice, William Plimley, after objections from several senators and New York bank presidents to the appointment of a political aide who had no relevant experience. Roosevelt then nominated Fish, who was promptly confirmed. He resigned from the Treasury in 1908 to run for the United StatesHouse of Representatives against Andrew C. Zabriskie. He defeated Zabriskie and was elected to represent New York's 21st district and served for a single term from March 4, 1909, until March 3, 1911. He was defeated for reelection. For many years Fish was considered to be one of the top Republican bosses in the State of New York, controlling Putnam County.
Personal life
In 1880, Fish was married to Emily Maria Mann at St. John's Church in Troy, New York. She was the daughter of Francis N. Mann and Mary J. Mann. Before her death in 1899, they were the parents of:
Emily Rosalind Fish, who married John Wilson Cutler, an investment banker, in 1910.
Hamilton Stuyvesant Fish III, also a U.S. Representative, who married Grace Chapin Rogers, daughter of Brooklyn Mayor Alfred C. Chapin in 1921. After her death in 1960, he married Marie Blackton in 1967. After her death in 1974, he was married to Alice Desmond from 1976 until their divorce in 1984. He married for the fourth time in 1988 to Lydia Ambrogio, whom he remained married to until his death at the age of 102.
Helena Livingston Fish, who married Henry Forster, a son of Frederick Prentiss Forster and Edith Forster, in 1920.
Through his daughter Julia, he was the grandfather of William Lawrence Breese Jr., founder and chairman of the Longview Foundation for Education in World Affairs and International Understanding, and Hamilton Fish Breese. Through his son Hamilton, he was the grandfather of Hamilton Fish IV, a thirteen-term U.S. Representative from New York who held office from 1969 to 1995, and Lillian Veronica Fish married David Whitmire Hearst, son of William Randolph Hearst.