William Belknap was an American politician who served as the Secretary of War under President Ulysses S. Grant from 1869 to 1876. He was born on September 22, 1829, in New York and had a background in law and politics. Belknap played a significant role in the post-Civil War military policies and was involved in various reforms during his tenure. In 1876, Belknap resigned amid a scandal involving corruption and the misappropriation of funds related to military contracts. Following his resignation, he was impeached by the House of Representatives but was acquitted by the Senate, which set a precedent for future impeachment cases. He died on October 13, 1890.