Martin T . McMahon Martin Thomas McMahon ( March 21 , 1838 – April 21 , 1906 ) was an American jurist and a Union Army general during the American Civil War . He was awarded the United States military ' s highest decoration , the Medal of Honor , for his actions at the Battle of White Oak Swamp . After the war , he held various legal and judicial positions in the state of New York . He briefly served as the Minister Resident to Paraguay and was a New York State Senator for four years . Early life . McMahon was born in Laprairie County , Quebec , Canada , to a family of recent immigrants from Waterford , Ireland . The family moved to the United States when McMahon was an infant and settled in New York . He graduated from St . John ' s College , Fordham , in 1855 and then studied law in Buffalo , receiving his Master ' s Degree in 1857 . After his schooling , he traveled west and worked as a special agent for the post office on the Pacific coast . He was admitted to the Sacramento , California , bar in 1861 . Civil War . At the outbreak of the Civil War , he raised a company of cavalry and was given the rank of captain at the head of that unit . After learning that his company would not be sent to the front lines , he resigned his command and returned east , where he was appointed aide - de - camp to General George B . McClellan . McMahon remained with the Army of the Potomac throughout the war , eventually rising to the rank of brevet major general . Decades after the end of the conflict , in 1891 , he was awarded the Medal of Honor for his actions at the Battle of White Oak Swamp on June 30 , 1862 . His official citation reads : " Under fire of the enemy , successfully destroyed a valuable train that had been abandoned and prevented it from falling into the hands of the enemy . " McMahon ' s two older brothers were also officers in the war , both with the 164th New York Volunteer Infantry Regiment . John Eugene McMahon ( 1834 – 1863 ) commanded the 164th before being injured ; he later died of these injuries . Middle brother James Power McMahon ( 1836 – 1864 ) took over the regiment and led it until his death at the Battle of Cold Harbor . In 1866 , after the end of the war , McMahon resigned his Army commission and received a Doctor of Laws degree from St . John ' s College , Fordham . He was New York City ' s corporation counsel for two years before becoming the United States minister to Paraguay , a position he held from 1868 to 1869 . After returning to the U . S . , he served as the Receiver of Taxes in New York from 1873 to 1885 and then worked as a U . S . Marshal for four years . During this time he became connected with the National Soldiers ' Home , of which he would serve as president for several years . Political career and death . He was a member of the New York State Assembly ( New York Co . , 7th D . ) in 1891 ; and of the New York State Senate from 1892 to 1895 , sitting in the 115th , 116th ( both 8th D . ) , 117th and 118th New York State Legislature s ( both 7th D . ) . He was elected a judge of the Court of General Sessions in 1896 and held that position until his death . He died suddenly in 1906 at his home in Manhattan , one day after falling ill with pneumonia .