Though many details about his early life are in dispute, scholars agree that Arnold was born in New York City and that his father may have been the Reverend George B. Arnold. The family relocated to Illinois and then to Monmouth County, New Jersey where Arnold enjoyed a country upbringing. Though he apprenticed himself to a portrait painter in New York in 1852, Arnold soon determined that literature would be his true calling.
While not much is known about the early life of Edward Mallen, he is remembered as an artist and frequenter of Pfaff's. William Winter identifies "Edward F. Mullen" as one of the artists who frequented Pfaff’s Cave along with Launt Thompson, George Boughton, and Sol Eytinge, Jr. (Old Friends 66, 88). Walt Whitman, a close friend of his, is also quoted as saying that "Mullin" was "among the leaders" at Pfaff’s (Bohan 134; T. Donaldson 208-209).