Windom was however elected to the regular full term that started March 4, 1871. He served from to March 7, 1881 when he was appointed as United States Secretary of the Treasury by PresidentJames Garfield and served from until he resigned from the Cabinet effective November, after having again been elected Senator on, to fill the vacancy caused by his own resignation, and served to March 3, 1883. He was an unsuccessful candidate for reelection in 1882. He moved to New York City in 1883 and practiced law. He was appointed Secretary of Treasury again in the Cabinet of President Benjamin Harrison and served from March 1889 until his death in New York.
Upon his death in 1891, the two-dollar silver certificate was redesigned with his portrait. This design was used from 1891 to 1896.
Windom invited the banks of the country to exchange their higher interest bonds for new bonds, bearing a much lower rate of interest.
Windom's maneuver was successfully executed at a cost to the government of about $10,000, while the saving effected in the annual interest charge was in excess of $10 million.
Windom resigned from the Cabinet upon the death of President Garfield, who was assassinated by a disgruntled office-seeker in November1881.