After 36 days at sea, an 11-year old Edgar A. Poe returned to the United States on July 21, 1820. The ship, named Martha, left Liverpool on June 16; it docked in New York City just over a month later and, as the local newspaper reported, passengers included "J & F Allan, E A Poe," and others. "J & F Allan," of course, are John and Frances Allan — Poe's foster-parents.
John Allan brought the family to England to expand his mercantile business in 1815, shortly after trade was re-opened after the War of 1812. Poe spent five of his most important formative years abroad. He visited Scotland (where his foster-father was born) and was educated in several London schools, including a boarding school at Stoke Newington run by Rev. John Bransby (an experience later fictionalized in "William Wilson"; the character in that story also has a schoolmaster named Bransby).
For the Allan family, the five years in England were not successful. Frances Allan's health continued to deteriorate (in fact, in 1819, a year before their return trip, John Allan reported "Frances begins to think she will never be able to cross the Atlantic"; she dies ten years later) and the Liverpool branch was not prospering.
Nevertheless, the experience overseas must have been influential on the young Poe. Though several other American writers spent time in Europe (especially Washington Irving — who dined with John Allan while overseas — as well as Henry Wadsworth Longfellow, Nathaniel Hawthorne and James Russell Lowell), each of them visited in their adult years; only Poe spent a major portion of his childhood there. Though he would never return to Europe, his first-hand experience with long sea voyages likely inspired his later fictional sea tales, most notably The Narrative of Arthur Gordon Pym of Nantucket.