Q152. "Why did the Convention take place in Philadelphia?"
A. An excellent question. Of course, there was no Washington, D.C. at the time — that plot of land was mostly a swamp. But there were cities other than Philadelphia. The Congress was meeting in New York City at the time of the Constitutional Convention, so it might have been a logical choice. Annapolis, Maryland, was another former home of the Congress. Boston was also a major city of the time, a hub of commerce.
But Philadelphia was special. For one thing, it was the biggest city in the United States at the time, and home to some of the new nation's most prominent citizens, including Benjamin Franklin. It had many features, some influenced by Franklin himself: libraries, theaters, poets, newspapers, and magazines. It was centrally located for most potential delegates (it is about as far from North Carolina as it is from New Hampshire). It also hosted the Congress for a very long time.
But it was also a hub of the American spirit — the birthplace of the nation, where the Declaration of Independence was signed. When the delegates to the Annapolis Conference met and wrote up the recommendation for the Convention, Philadelphia was specifically mentioned as the meeting place. The delegates to that conference were not fools. They immediately lent gravitas to the Convention by holding it in Philadelphia, and in doing so, attracted many of the nation's most prominent citizens.