In 1831 he joined the First Presbyterian Church, decided to become a minister, and returned to the East to study at Princeton Theological Seminary. He was licensed to preach in April, 1833, by the Second Presbytery of Philadelphia. He was ordained by the Presbytery of St. Louis in 1834 and was elected its Moderator in 1835. In St. Louis he was pastor of the Des Peres Presbyterian Church (the "Old Meeting House"). He published a religious newspaper, The St. Louis Observer, and began to advocate the abolition of slavery. Despite the bitter feeling against him., Lovejoy persisted in arguing the fights of freedom of the press, freedom of speech, and freedom from slavery. After seeing a slave, Francis J. McIntosh, burned at the stake, his editorials became so strident against slavery that he became an object of hatred by both Southerners and slave-holders. His press was wrecked by a mob in July, 1836, and he moved to Alton in the free State of Illinois.
In Alton, Lovejoy became the Stated Clerk of the Presbytery in 1837 and the first pastor of the present College Avenue Presbyterian Church. He actively supported the organization of the Ant-slavery Society of Illinois which enraged the Alton citizens. He continued writing and publishing the Alton Observer even after three presses had been destroyed and thrown into the Mississippi River.
On the historic night of November 7, 1837, a group of 20 Lovejoy supporters joined him at the Godfrey & Gilman warehouse to guard a new press until it could be installed at the Observer. As the crowd grew outside, excitement and tension mounted. Soon the pro-slavery mob began hurling rocks at the warehouse windows. The defenders retaliated by bombarding the crowd with a supply of earthenware pots found in the warehouse. Then came an exchange of gunfire. Alton's mayor tried in vain to persuade the defenders inside to abandon the press. They stood fast. One of the mob climbed a ladder to try to set fire to the roof of the building. Lovejoy and one of his supporters darted into the darkness to over-turn the ladder, for they knew they would be doomed if a fire was set. But again a volunteer mounted the ladder to try to ignite the roof with a smoking pot of pitch. As Lovejoy assisted Royal Weller in putting out the fire on the roof of the building, Lovejoy received a blast from a double-barreled shotgun. Five of the bullets fatally struck Lovejoy. He died in the arms of his friend Thaddeus Hurlbut. The mob cheered and said all in the building should die. Amos Roff tried to calm the mob and was shot in the ankle. Defenders of the press then laid down their weapons and were allowed to leave. The mob rushed the building, found the press, and threw it out a window to the riverbank, broke it into pieces and dumped the broken parts into the river, The body of Lovejoy was left undisturbed, remaining there until morning, guarded by friends who finally carried him home. He was buried on his 35th birthday, November 9, 1837, in an unmarked grave in the Alton City Cemetery, the location known by a black man, William "Scotch" Johnston, who assisted in the burial.
(Account of the evening as reported by the Alton Observer)
Years later, through the generosity of Thomas Dimmock, Lovejoy's body was exhumed and reinterred at the present site. Dimmock purchased the small but appropriate marble scroll which marks the grave on which is inscribed the Latin words which translates:
"Here lies Lovejoy - Spare him now the grave." He also purchased the New England granite block beneath the scroll and the wall which encloses the grave site.
The story of Lovejoy and the Abolitionists is the story of the enduring vigil for freedom of thought, speech, and the press. For a moment in 1837, Alton, Illinois, was the scene of a battle for freedom that was felt across the nation. The mob action at Godfrey & Gilman warehouse was the first, but unrecorded, battle of the Civil War.