Taft was born into a powerful Ohio political family. His father Alonzo Taft later served as Attorney-General and Secretary of War in the cabinet of Ulysses Grant. His oldest son Robert was a well-known Senator who challenged Dwight Eisenhower for the Republican nomination for President in 1952 and as recently as 2007, Taft's great-grandson Bob Taft was Governor of Ohio.
As a young man, Taft was nicknamed "Big Bill" because of his size. He graduated from Yale College Phi Beta Kappa in 1878 and from Cincinnati Law School in 1880. Taft became a judge on the Ohio Supreme Court in 1887 and in 1890, he was appointed Solicitor General of the United States. In 1891 he was appointed a judge on the United States Court of Appeals for the Sixth Circuit.
In 1900, President William McKinley appointed Taft to be the Governor-General of the Philippines. Taft performed admirably in the task, maintaining order while showing benevolence to the locals. In 1904, President Theodore Roosevelt appointed Taft as Secretary of War in his cabinet, with the intention of grooming Taft, then his close political ally, into his handpicked presidential successor. Riding a wave of popular support for his fellow Republican Roosevelt, Taft won an easy victory in his 1908 bid for the presidency, defeating Democrat William Jennings Bryan in Bryan's third run for the Presidency.
In his only term as President, Taft's domestic agenda emphasized trust-busting, civil service reform, strengthening the Interstate Commerce Commission, improving the performance of the postal service, and passage of the Sixteenth Amendment (which gave Congress the right to levy a uniform income tax across the country.) On the international front, Taft promoted the economic development of underdeveloped nations in Latin America and Asia through what became known as "Dollar Diplomacy". He was almost assassinated on October 16, 1909 on a visit to Mexico, but the would be assassin was detected by alert security men. The man was arrested while holding a loaded pistol within a few feet of Taft and Mexican President Porfirio Diaz.
Many of Taft's policies were at odds with the wishes of his mentor, Theodore Roosevelt. Roosevelt was especially upset when Taft fired Roosevelt's good friend Gifford Pinchot from the position of Chief of the US Forest Service. When Roosevelt ran against Taft for the Presidency under the banner of a third party known as the Bull Moose Party, Taft was overwhelmingly defeated in in the presidential election of 1912, finishing third behind the winner Woodrow Wilson and behind Roosevelt's Bull Moose Party.
After leaving office, Taft taught law at Yale and was elected President of the American Bar Association. He founded the League to Enforce Peace, an organization dedicated to the promotion of world peace. In 1921 President Warren G. Harding appointed Taft Chief Justice of the United States. Taft served in this capacity until shortly before his death in 1930. He is the only former president to administer the oath of office to another President and the only Chief Justice to serve with associate justices whom he had appointed to the court.
Taft thus far was the largest man to hold the office of President. At just under 6 feet tall, he weighed as much as 343 pounds during his presidency. He suffered from severe obstructive sleep apnea because of his obesity. Within a year of leaving the presidency, Taft lost approximately 80 pounds causing his blood pressure to drop and his sleep problems to end. Soon after his weight loss, he had a revival of interest in the outdoors and this led him to explore Alaska.
Taft retired as Chief Justice on February 3, 1930, because of ill health. Charles Evans Hughes, whom he had appointed to the Court while president, succeeded him. Five weeks after his retirement, Taft died on March 8, 1930. On March 11, he became the first president to be buried at Arlington National Cemetery.