Born in Chester County, Pennsylvania, he worked as a wholesale grocer and lawyer. He had been director of the Commercial National Bank of Chicago for 29 years when PresidentWilliam Howard Taft asked him to be Secretary of the Treasury in 1909. He did not tackle the pressing problem of currency reform, leaving it to the National Monetary Commission, which had been established by the Aldrich-Vreeland Act of 1907. He did, however, stress the urgency of reform in his annual report. He is remembered for increasing the efficiency and general progressiveness of the Treasury Department: He abolished 450 unnecessary positions, rehabilitated the U.S. Customs Service with the introduction of electric automatic weighing devices and accepted certified checks instead of currency for customs and internal revenue payments. He was also involved in the creation of the buffalo nickel.
MacVeagh was U.S. ambassador to Turkey in 1870 through 1871, and was a member of the state constitutional convention of 1872 and 1873.
He also served as chairman of the MacVeagh Commission, sent in 1877 by President Rutherford B. Hayes to Louisiana, which secured the settlement of the contest between the two existing state governments and thus made possible the withdrawal of U.S. troops from the state.