Probably my single biggest pet peeve: the common misspelling of Poe's "middle" name. The name is Edgar Allan Poe. That middle word has two A's, no E's. And here's the story behind it (and, maybe, why we shouldn't call him that)...
On January 7, 1812,* a very young Edgar Poe was christened into the Episcopalian church. His sponsors were John and Frances Allan of Richmond, who had only recently taken the young boy in as their ward. Almost exactly one month earlier, Poe's mother Eliza had died and he and his two siblings were split to various families. Young Edgar was taken in by the Allans mostly through the goading of Frances. His life with the soon-to-be wealthy Allans started off promising: during his christening, he was given the name "Edgar Allan Poe". Such promise was never fulfilled; he was not formally adopted and maintained his status as "foster" son. The name from his christening, of course, was also never made legal; in other words: the man's name was (and is) "Edgar Poe."
Though both Poe and his foster-father John Allan made attempts to make the relationship work during Poe's childhood, it never really came to be more than a formal arrangement. In England, Poe was enrolled in school as "Edgar Allan" but, the truth is, Poe didn't care much for his pseudo-connection to the Allan family, particularly John Allan.
By the time his writing career began, he was Edgar Poe or, perhaps, Edgar A. Poe. There are only two or perhaps three occasions where he purposely used the now-standard three-word moniker "Edgar Allan Poe" — and once it was while soliciting John Allan for a loan. Ultimately, I would suggest that Poe's christening on this day in 1812 was not the day where the name Edgar Allan Poe was created as a standard.
I might suggest it was not until that certain now-famous article on October 9, 1849, that the name popped into the collective mind. The article which shocked the literary community and made the rounds nationwide was Poe's obituary. It began: "Edgar Allan Poe is dead." Its author was influential, combined with the sensationalism in his portrait, made it a household name. What would Poe himself say? But, this might be a story to consider in October.
*The date comes from Dawn Sova's Edgar Allan Poe: A to Z. The Allans would have had Poe for only a short time before rushing him to this ritual. If the date is correct, it might indicate a chance for Poe to be brought into the family as more than just a foster son. If anyone has evidence why we should be skeptical of the date, please let me know!