Abraham Alfonse Albert Gallatin ( January 29 , 1761 -- August 12 , 1849 ) was a Swiss-American ethnologist , linguist , politician , diplomat , Congressman , and the longest-serving United States Secretary of the Treasury . Abraham Alfonse Albert Gallatin ( January 29 , 1761 â `` August 12 , 1849 ) was a Swiss-American ethnologist , linguist , politician , diplomat , congressman , and the longest-serving United States Secretary of the Treasury .