He joined the Seventeenth Infantry Regiment of the United States Army as a Second Lieutenant in 1899, after the United States had occupied the Philippine Islands in the Spanish–American War. In the course of nearly four years in the Philippines, he served under General Arthur MacArthur, Jr., was on the staff of General Leonard Wood during the Moro rebellion, and commanded a battalion of Philippine Scouts. He resigned from the Army in 1905 with the rank of Captain, and became New York's First Deputy Commissioner of Police in January 1906, at the age of 28. Waldo, who had served as New York City Fire Commissioner since the beginning of Mayor Gaynor's term in January 1910, was in office at the time of the Triangle Shirtwaist Factory fire which occurred on March 25, 1911 and killed 146 people. On June 9, 1911, only 17 days after taking office as Police Commissioner, Waldo founded the motor-cycle squad, organized under the Office of Street Traffic Regulation Bureau. Another of his early acts as Police Commissioner was the appointment of three "Strong Arm" anti-vice squads and their commanders—one of whom, Charles Becker, was later executed for complicity in the July 1912 murder of the bookmaker Herman Rosenthal. Acting Mayor Ardolph Kline's elected successor, John Purroy Mitchel, indicated before taking office at noon on January 1, 1914, that he would not keep Commissioner Waldo in office. Waldo tendered his resignation effective at midnight December 31, 1913, after transferring or accepting resignations from most of the department's senior officers and specialists. Amid much confusion and discord, Mayor Kline refused to accept Waldo's resignation and fired him instead.
Later career
In 1916, Waldo held a commission as Major in the Infantry Officers Reserve Corps. He went into World War I as a Major in the 301st Infantry of the National Army in 1917. After serving in France, he was honorably discharged in 1919 and in 1923 was commissioned a Colonel in the reserve. After he was out of office, he stayed involved with political affairs and while Richard Enright was New York City Police Commissioner, Waldo served for a time as a special deputy but resigned in September 1924 to organize the Coolidge Nonpartisan League, a step that "marked his formal renunciation of Tammany Hall in favor of the Republican Party." Around this time, he was mentioned as a possible candidate for Governor General of the Philippines.
Personal life
On April 20, 1910, he was married to Virginia Otis Heckscher at the country house of artist Charles H. Ebert in Greenwich, Connecticut. Virginia, a daughter of Robert M. Otis and Helen Otis of Richmond, Virginia, was twice widowed before their marriage. Her second marriage was to John Gerard Heckscher who died in 1908. He died on August 13, 1927 in his home in Philipse Road in Garrison, New York of sepsis.
In popular culture
Waldo was portrayed by James Cagney in the 1981 film Ragtime, despite the age difference However, in E.L. Doctorow's original 1975 novel Ragtime from which the film was adapted, Waldo's role in the narrative is minor while Charles S. Whitman, the real-life Manhattan District Attorney at the time, performs most of the fictional words and deeds that the film would later assign to Waldo.