Poe began a lecture tour on November 21, 1843 in Philadelphia. The broad topic was "The Poetry of America." This was an era of oratory and many writers knew that lectures and public readings would greatly boost their income. Other writers turned lecturers included James Russell Lowell, Oliver Wendell Holmes, and, of course, Ralph Waldo Emerson, who was so successful as a lecturer it qualifies as his full-time job.
The purpose of this particular lecture was for Poe to discuss the state of American poetry and his literary theories. However, he couldn't resist wielding his tomahawk as a critic. He focused on the poor taste of his critical rival Rufus Wilmot Griswold, whose book The Poets and Poetry of America was published a year earlier and was clearly referenced in the lecture title. One periodical later noted "this book and its author were handled by the critical Lecturer in not the most gentle manner" (what a great euphemism!).
This could be yet another minor reason why the two men would build a major rivalry/enmity for one another. It was shortly after this, in January 1844, that Griswold wrote to Poe about "some cause of personal quarrel with you, which you will easily remember."
One review later remarked that the lecture "placed all the pseudo-critics, the Rev. Mr. Rufus Griswold, Esq. among others, to the blush."
Poe's lecture in Philadelphia was very successful. The Saturday Museum noted it had "quite a large, and certainly highly intelligent audience." According to the United States Gazette, "hundreds" were turned away, "unable to gain admission." The Saturday Courier noted that "it was a very learned critique, marked by the severity of illustration for which the author is so ably known."
Over about four months, Poe also lectured on the same topic in Reading, Pennsylvania and Baltimore, as well as Wilmington and Newark, Delaware. He begins another lecture tour on a similar topic in 1845, culminating in his strange appearance at the Boston Lyceum.