Peter Hagner (October 1, 1772 – July 16, 1850) was a clerk in the accounting office of the United States War Department, 1793–1817, and Third Auditor of the United States Department of the Treasury from 1817 to 1849; he served during the administrations of every president from George Washington to Zachary Taylor and was known as the "watchdog of the Treasury.
[2] In 1793, Hagner was appointed a clerk in the United States Department of War by President George Washington and appointed an assistant accountant in 1797, and Third Auditor of the United States Treasury by James Monroe when that office was created in 1817.
[2] Twice by direct votes the U. S. Congress expressed its appreciation of his services in the settlement of large and important claims.
This office became at one time so prominent, from the calls made upon its chief by Congress, before the institution of the court of claims, that John Randolph of Roanoke, pausing in debate for a phrase to express his sense of the influence of Nicholas I of Russia in the affairs of Europe, styled him "the great third auditor of nations.
[21] Through his son Daniel,[22] he was a grandfather of Belle Hagner (1875–1943), who was the first White House Social Secretary, serving in the administrations of President Theodore Roosevelt, William Howard Taft, and Woodrow Wilson.