In 1901, he was appointed assistant corporation counsel of New York County, New York. He was next elected as city magistrate. In this capacity, he founded the Night Court for the immediate trial of all offenders arrested at night. In 1907, GovernorCharles Evans Hughes appointed Whitman as a judge of the Court of Sessions. The following year Hughes appointed him as deputy state attorney general in the investigation of election frauds in northern New York.
In 1909, Whitman was elected as New York County District Attorney on a Fusion ticket. In this capacity, he secured representation of the District Attorney's staff in the city magistrate's office. He was also known for his vigorous prosecution of arson offenders, which contributed to a decline in such fires. As District Attorney, Whitman gained national fame in prosecuting New York City Police Lt. Charles Becker for the July 16, 1912, murder of Herman Rosenthal, a Times Square gambling house operator, in front of the Hotel Metropole on West 43rd Street. The building was owned by "Big Tim" Sullivan, a leader of the Lower East SideTammany Hall political machine. During this period, Whitman used his membership in the Union League Club of New York to conduct secret interviews there of witnesses during the Becker case, as he feared he was under surveillance. Whitman's prosecution revealed the corrupt relations between certain members of the New York City police and professional criminals, and resulted in reforms of the police. Becker was convicted in a jury trial and sentenced to death. Later, as governor, Whitman signed Becker's death warrant and presided over his electrocution. Whitman's handling of the murder case of Hans Schmidt, a priest, and his prosecution of the poultry trust and of election frauds also gained him high praise. After being renominated for District Attorney in 1913, he was elected almost unanimously.
Whitman was elected in 1914 as the 41st Governor of New York, serving from January 1915 to December 1918. His principal plank was the reformation of the state finances. He reorganized state departments and conducted a thorough investigation of the salaries of civil service employees. In 1915, he became a member of the Empire State Society of the Sons of the American Revolution. This lineage society was based on descent from men who had served with the patriots in the revolution. In 1916, Whitman won re-election as governor against reform Democrat Judge Samuel Seabury. After his election, he sent a report of his first term as governor to every registered voter; it included reports of the heads of his state departments. He also inaugurated a state constabulary. After the United States entered into World War I, Whitman established a new state guard to replace the National Guard, which was on service in France. In 1916, he was elected as chairman of the Republican National Convention, where he urged the nomination of former New York Governor Hughes for President of the United States. In 1917, he commissioned the creation of the New York State Police and selected George Fletcher Chandler, a physician and major in the National Guard, to organize and head the force. In 1918, Whitman was defeated for re-election by Democrat Alfred E. Smith. Smith drew from the growing strength of recent immigrants and their descendants.
Personal life
In 1908, Whitman was married to Olive Hitchcock. Together, they were the parents of:
Olive Whitman
Charles S. Whitman, Jr,, who was a New York Judge.
After the death of his first wife in 1928, in 1933 he married Thelma Somerville Grosvenor, the widow of Edwin Prescott Grosvenor, himself the son of Edwin A. Grosvenor and brother of Gilbert Hovey Grosvenor. He died on March 29, 1947 in Manhattan.