A native of Islip, Long Island, New York, and a graduate of West Point, William Ludlow was a veteran of the Civil War. In May 1898, he was named brigadier general of volunteers and commanded the First Brigade at El Caney in Henry Lawton's division in Cuba. As ranking overseas engineer, he was in charge of the embarking of General Calixto García's forces at Aserraderos. In September 1898 Ludlow was promoted to major general of volunteers and in January 1900, he received the rank of brigadier.
Following the war, he held the post of military governor of Havana. He also served on a board of officers, later named for him, that advised the establishment of an Army War College in 1900. He died in August 1901.