Gorman was originally a lawyer by profession, graduating from the University of Indiana law school. He began to practice in Bloomington, Indiana, in 1835. By 1837 he began his move into politics, becoming a clerk in the state senate, to which he was later elected several times. In 1846 he volunteered for the army, and went to fight in the Mexican-American War. In 1848 he was civil and military governor of Puebla, but soon after he returned to Indiana. He served in the United States House of Representatives from March 4, 1849 to March 3, 1853 as a representative of that state, then served as the second Territorial Governor of Minnesota from May 15, 1853 to April 23, 1857 at the appointment of President Franklin Pierce. During his time as Governor of Minnesota, he masterminded an unsuccessful plan to move the capital of the territory from St. Paul to St. Peter, where he owned land that would have been eminently suitable for use as the new capitol grounds. The plan was sidetracked when legislator Joe Rolette disappeared with the bill until the last seconds of the legislative session. After a number of years practicing law in St. Paul, Minnesota, he was made colonel of the 1st Minnesota regiment, serving in the First Battle of Bull Run on July 21, 1861. On September 7, 1861, he was appointed brigadier-general of volunteers. In 1864 he left the service and resumed his law practice in St. Paul. He was elected City attorney in 1869, and continued in that position until his death on May 20, 1876.