Jakob Rapp was born around 1828 in present-day Baden-Wurttemberg, Germany. He got married, and he had at least four children, including Elias, who was born around 1847. He eventually immigrated to America and settled in Rhinebeck, New York. He earned a living as a teamster.
He enlisted in the Union army on September 5, 1862, and he mustered in as a private in Company K of the 150th New York Infantry. According to his service records, he was 5 feet, 8 inches tall, with brown hair and blue eyes. In December 1862, he expressed disillusionment with the Union war effort. When a friend wrote that “we have to whip the South,” Rapp replied, “i think now we cant doe ite by fighting.” He added that he “like[d] Soldiern first rate so far but i would like ite better at home.” He deserted on February 7, 1863.
He was drafted into the Union army soon afterward, and he mustered in as a private in Company H of the 97th New York Infantry on August 19, 1863. The regiment took part in the Overland Campaign, the siege of Petersburg, and the Appomattox campaign. He mustered out on July 18, 1865. He died sometime after the war.