Judge, and United States Senator, was one of his instructors. Judge McDill said “he was an eccentric young man, quiet and very studious.” But he had no taste for the orthodox ministry. In an essay he declared his belief in universal salvation and soon after became a Spiritualist. In 1857, Jeremiah went to Kansas and took a claim on the Little Osage. He joined Colonel Montgomery’s army and fought with him to make Kansas a free State. He afterward served under John Brown and was with him in one of his successful incursions for the liberation of Missouri slaves. He again joined his old commander in New York, where he was organizing the Harper’s Ferry campaign and was one of his most trusted and faithful friends. John Brown told Gerrit Smith that “Anderson was more than a friend; he was as a brother and a son.” Three days before his execution Captain Brown said: “My brother Jeremiah was fighting bravely by my side at Harper’s Ferry up to the moment when I was struck down.” When Colonel Lee’s marines broke through the barricade and charge on its five defenders, Anderson was pierced with three bayonets as his smoking rifle fell from his grasp. Mortally wounded he was dragged out by his captors, thrown down on the stone flagging and left to the mercy of the brutal crowd. He lingered there in great agony for three hours, subjected to the most fiendish tortures. A gang of Virginia “chivalry” now mustered courage to approach the disarmed and dying man, kicking his face with their heavy boots, then opening his eyes, they spat tobacco juice into them, while others forced their filthy quids into his mouth amid laughter, jeers and horrid oaths. When death finally ended his sufferings, two village doctors came and crowded his mutilated body into a salt barrel, stamping it down with their feet. They carted their prey toward their office and that was the last seen of Jeremiah G. Anderson, the close friend of John Browns and one of the bravest Iowa soldiers who ever marched to the field of death.
