Civil War hero and secretary of war under President Ulysses S. Grant—was born in Newburgh, New York, the son of a regular U.S. Army officer. He grew up in the East, graduated from Princeton University in 1848, and passed the bar in 1851 after studying at Georgetown University. Later that year, Belknap moved to Keokuk, Iowa, and took up the practice of law in partnership with Ralph P. Lowe, future governor of Iowa and chief justice of the Iowa Supreme Court. In 1857 Belknap was elected to the Iowa General Assembly as a "Douglas" Democrat. Along with the first of his eventual three wives, Cora Leroy, Belknap enjoyed considerable social standing as well as growing political prominence.
With the beginning of the Civil War, Belknap, by then a Republican, was commissioned as major in the 15th Iowa Infantry. His military career was brilliant from the beginning, and he advanced rapidly in rank and reputation. He was cited for bravery at Shiloh and Corinth and was singled out for an act of personal heroism during the siege of Atlanta in July 1864, having reached the rank of brevet colonel by that stage. He was then brevetted to the rank of brigadier general and given command of the four regiments of the famous Crocker 's Brigade. He led his men on Sherman's March to the Sea and was promoted to brevet major general at the end of the war. Offered a regular army commission, he declined and instead returned to Keokuk. Based on his war record and his Republican connections, he was named to the coveted office of Collector of the Internal Revenue for Iowa's First District.
Cora had died during the war; in 1868 Belknap married a Kentuckian, Carita Tomlinson. The following year, on the recommendation of Belknap's former commander, William T. Sherman, newly elected President Ulysses S. Grant named Belknap secretary of war, the third-highest ranking cabinet post, responsible not only for the national armed forces, which were drastically reduced following the war, but also administering army posts and the American Indian trade in the West.
Moving to Washington, D.C., William and Carita became leading figures in the capital's postwar society. They established a fashionable and lavishly appointed home and entertained on a grand scale. Unfortunately, Carita was in delicate health, and she died not long after giving birth to a son, Robert, who himself died five months later. Two years later Belknap took Amanda "Puss" Tomlinson, his second wife's sister, as his third wife, and the couple assumed life near the top of Washington's social pyramid.
To all public appearances, Belknap's term as secretary of war was uneventful until 1876. He kept a relatively low professional profile and seemed to have escaped the scandal and corruption at the top of the administration that emerged during Grant's second term in office. But on March 2, 1876, Belknap's old college roommate, Hiester Clymer, a Democratic congressman from Pennsylvania, interrupted debate in the House of Representatives to report as chair of the House Committee on Expenditures in the War Department. Clymer declared that his committee's hearings had uncovered "unquestioned evidence of the malfeasance in office by General William W. Belknap."?Although Belknap had resigned a few hours before the accusations were made, Clymer moved that Belknap be impeached.
As the preponderance of testimony and evidence came to show, Belknap had apparently profited from a scheme to sell the Indian post tradership at Fort Sill, Indian Territory, to Caleb P. Marsh, a New York businessman. The deal had been struck indirectly in 1870 by Carita Belknap, the secretary's second wife, who cautioned Marsh to negotiate through her and to avoid direct discussions of the post tradership with Belknap. Although the ar rangements were complicated, Marsh eventually paid $20,000 over five years directly to Belknap, who signed receipts for the money. Subsequently, Belknap and his supporters claimed that the secretary thought the money came from private investments Puss had placed with Marsh.
When Marsh was called to testify to Clymer's investigative committee in late February 1876, Belknap realized he was caught. He managed to get his resignation in to President Grant just before Clymer could call for his impeachment. Despite claims by his few supporters that his resignation removed him from Congress's jurisdiction, he was im peached unanimously by the House. A week later he was also indicted on civil charges and placed under house arrest.
After weeks of further investigation by the House committee, including testimony by General George A. Custer, on his way to an appointment in July with several thousand Sioux warriors at the Little Big Horn, the Senate convened a trial of Belknap, spending several more weeks discussing whether the senators had jurisdiction. When direct arguments began, Belkap's attorneys relied mostly on the argument that he could not be convicted because he had resigned before the articles of impeachment had been formally brought against him. In the end, enough senators agreed to let Belknap escape. Twenty-five of 60 senators voted not guilty on technical grounds–leaving the vote short of the required two-thirds–although 23 senators publicly declared that they thought him guilty in fact. All senators agreed he had taken the money.
Following the trial, Puss and her daughters moved to Paris, France, where they remained until after Belknap's death. The former secretary himself moved to Philadelphia in the immediate aftermath of his disgrace but eventually returned to Washington and quietly practiced law until his death.
Belknap remained a hero to his former Civil War army colleagues, despite his public dishonor, and in later years the veterans of Crocker's Brigade raised an impressive monument to Belknap, including a bas-relief portrait at his grave in Arlington National Cemetery.