Jacob is an American No-Maj factory worker who lived in 1920's New York City. Prior to the events of Fantastic Beasts, he previously fought for the United States Army in World War One. After the war, he sought work at a factory in New York, but actually dreamt of becoming a baker.
Shortly after breaking up with his ex-girlfriend in 1926, he met British magizoologist Newt Scamander (through him, he was introduced to the Wizarding World in America), and accidentally opened his magical briefcase, unleashing a plethora of magical beasts that could potentially strain the already frail relations between the Magical and Muggle Communities in the United States, and he was nearly attacked by a murtlap. He also fell in love with Queenie Goldstein.