He had been appointed Internal Revenue tax collector in Iowa by President Johnson after the Civil War and remained in this position until  President Ulysses Grant appointed him to head the War Department in 1869.

He had held his cabinet post for nearly eight years from October 25, 1869 – March 2, 1876 before the scandal erupted

He was known for his extravagant lifestyle and giving expensive parties. People wondered how he could afford the luxuries on his $8000 a year salary

Political corruption was rife and a House of Representatives’ committee started to investigate the activities of the U.S. Secretary of War and his luxurious lifestyle

On February 29, 1876, Congress launched an extensive investigation run by Hiester Clymer

The committee uncovered evidence of widespread corruption in which it became clear that William Belknap had accepted bribes from companies with licenses to trade on the reservations of many Native American Indian tribes.

Belknap had been given sole authority to appoint Indian post-traderships by Congress

He abused the power of his position and accepted illicit kickbacks or bribes in exchange for making lucrative Indian tradership appointments

The corruption had started in 1870 when he (and his first and then second wife) took quarterly payments for the Fort Sill "tradership" position awarded to Caleb Marsh and a sutler called John Evans. Caleb Marsh gave kickbacks to the Belknaps totally of $20,000.

Fort Sill, in Oklahoma Indian Territory, afforded a highly lucrative military contract. Belknap went on to empower the traderships even further by giving them a virtual monopoly over trade.

Sutlers, men who sold provisions to the soldiers, were appointed to operate in the Military and Indian traderships

The US Soldiers stationed at forts operated by Belknap appointed sutlers could only buy supplies through the authorized tradership. This monopoly enabled the sutlers to charge highly inflated prices for the necessary supplies

The sutlers also made even more profits from Native American Indians by selling rifles as well as basic supplies.

Rumors of the corruption led to a political scandal. The leader of the investigating Committee, Hiester Clymer, was a staunch Democrat who vehemently opposed Republican Reconstruction of the Grant administration

Caleb Marsh gave evidence that Belknap had accepted payments in return for trading partnerships between himself and the sutler John Evans.

In light of the evidence stacked against his Secretary of War, President Grant asked for his resignation, which was given

Despite his resignation from the cabinet the Committee started impeachment proceedings.

As he resigned before the Impeachment trial (as would Nixon in later years) he was acquitted on the grounds that the Senate lacked jurisdiction after his resignation had been accepted. No civil charges were made against him.