I'm not familiar with the history of Md. or Pennsylvania. Perhaps a study of those two states during that period may help to understand why they left the US for Haiti.

It's intriguing (their journey to Haiti) to learn why they went all the way to Haiti after living in Philadelphia. I've studied the migration of slaves and free people of color of the Lower South to the places that you mentioned...Mexico, Cuba, Haiti etc.

I guess you may want to know WHY.

You wrote "Someone told me I should try to find their port of reentry to the U.S."

That someone was correct. Here is what I found from the Ancestry database.

New York Passenger list

Noah King
Arrived 12 Jun 1869
abt 1824
Port Au Prince, Haiti
American
Brig: Henry and Louis

Noah King is listed as a servant.
Jane King (30 yrs.) female servant
William King (5years)
Joseph McLaughlin (no age)

Mr. M, Hudson Occupation: Merchant?
Mrs. Mary Hudson

There are 42 Guillory names from St. Marc Haiti. (1870)

I hope this helps.

K Wyer Lane