 In 1845, during a stop in Charleston, South Carolina, Petersen heard a series of sermons that brought him to a consciousness awareness of Methodism.He also came into contact with Swedish born pastor Olof Gustaf Hedström (1803–1877) who ministered among the sailors from the "Bethel Ship John Wesley", a former cargo ship in New York Harbor (1845–1875).In 1847, Petersen became a member of the Methodist Church's Bethel Ship Mission in New York and was employed as Pastor Hedström's assistant.