There are four major characters in the book. They are:
1) Lt. John (Jack) Worden, U.S. Navy. He becomes the first POW of the Civil War when the Confederates take him prisoner the day after the war begins. Released after seven months of incarceration, when both sides agree to an exchange of officers, he goes on to win honor and glory as skipper of the Monitor in her world-famous confrontation with the Confederate Merrimack.
Character and personality: Forty-three years old and a veteran of twenty-seven years, Worden comes of humble farming folk, is devout, bookish, abstemious, and a bit of a loner, with an excellent service record. Though he has earned a reputation for inspiring the loyalty, respect, and affection of his subordinares wherever he serves, his rise through the ranks has been slow. The reason is succinctly expressed by the Assistant Secretary of the Navy: "Sounds like an advanced case of no friends in high places."
Worden is married and the father of four children. His wife, Olivia, daughter of a wealthy and socially prominent New York family, is described as a woman of quiet beauty and extraordinary determination. She is instrumental in persuading the Navy to negotiate her husband's release from an Alabama POW camp.
2) Captain John Ericsson, brilliant naval architect and inventor, is regarded with suspicion and contempt by Navy brass who, unjustly hold him responsible for a tragic marine accident that has taken the lives of the Secretary of State and the Secretary of the Navy, among others. Ericsson, a proud and unbending man, does not deign to clear his name, and will have nothing to do with the Navy. Reposing on the inventor's shelf are his plans for an all-iron boat, half submarine, half gun platform, of which the Navy wants no part.
3) Secretary of the U.S. Navy, Gideon Welles, a feisty New Englander and former newspaper publisher is, above all, concerned with maintaining the all-important blockade of the southern coast. His main adversary, he finds, is not the Confederate fleet, but rather the tradition-bound Navy of which he is Secretary.
4) Abraham Lincoln on being shown a model of Ericsson's ironclad, expresses his opinion as a former riverboat pilot: "Well, all I have to say is what the girl said when she put her foot into the stocking, 'It strikes me there's something in it.'"