Seth Williams Seth Williams ( March 22 , 1822 – March 23 , 1866 ) was an American military officer who served as assistant adjutant general of the Union ' s Army of the Potomac during the American Civil War . Early life . Williams was born in Augusta , Maine . He graduated from the United States Military Academy in 1842 , 23rd in a class of 56 . He served as aide - de - camp to General Robert Patterson in the Mexican - American War with the rank of second lieutenant . Williams received a brevet to the rank of captain for his conduct at the Battle of Cerro Gordo as a first lieutenant . He was adjutant at West Point from 1850 to 1853 before moving to the adjutant general ' s office in Washington , D . C . . Civil War . Williams was promoted to the rank of major in August 1861 and lieutenant colonel on July 7 , 1862 . On September 28 , 1861 , President Abraham Lincoln appointed Williams a brigadier general of volunteers , to rank from September 23 , 1861 . President Lincoln nominated Williams for the promotion on December 21 , 1861 and the U . S . Senate confirmed the appointment on July 17 , 1862 . He was a groomsman at George McClellan ' s wedding in New York City on May 22 , 1860 . Seth Williams served as assistant adjutant general to Major General George B . McClellan in the Department of the Ohio in the summer of 1861 . From August 20 , 1861 to March 1864 , Williams was assistant adjutant general of the Army of the Potomac , responsible for the routine drafting of orders , correspondence , and reports . McClellan named him to that position after unsuccessfully requesting the assignment to Maj . Gen . Fitz John Porter . McClellan and Williams became friends during their service together . Williams was called before the United States Congress Joint Committee on the Conduct of the War to testify about the Battle of Gettysburg . Williams ' s testimony was especially helpful to Meade . Williams was a convivial officer to whose quarters other officers resorted for company . Williams later served as inspector general on the staff of Lt . Gen . Ulysses S . Grant from the spring of 1864 to February 9 , 1866 . When Grant decided to recommend surrender to Robert E . Lee during the Appomattox Campaign , it was Williams who took the message to the Confederate lines . He also delivered Grant ' s terms to the Confederate army . He was present at the surrender on April 9 , 1865 . Williams was awarded the brevet of colonel for the Battle of Gettysburg . On January 13 , 1866 , President Andrew Johnson nominated Williams for the brevet grade of major general of volunteers for his service in 1863 and 1864 , to rank from March 13 , 1865 , and the U . S . Senate confirmed the nomination on March 12 , 1866 . Although slated to begin service as assistant adjutant general of the Military Division of the Atlantic , Williams became ill later that month and left for Boston , Massachusetts . There he died of a brain ailment , described as an " inflammation " on March 23 , 1866 . He was buried in Augusta ' s Forrest Grove Cemetery . Fort Williams on Cape Elizabeth , Maine , is named for him . The name was assigned on April 13 , 1899 . On April 10 , 1866 , President Andrew Johnson nominated Williams posthumously for appointment to the brevet grade of brigadier general in the regular army , to rank from March 13 , 1865 and the U . S . Senate confirmed the appointment on May 4 , 1866 . On July 17 , 1866 , President Johnson nominated Williams posthumously for appointment to the brevet grade of major general in the regular army , to rank from March 13 , 1865 and the U . S . Senate confirmed the appointment on July 23 , 1866 . Popular culture . Gen . Williams was portrayed by actor Clarence Key in the Spielberg - directed biographical drama " Lincoln " ( 2012 ) .