The day before I read your brilliantly thoughtful and informative piece, I was thinking about my childhood in St. Louis, Missouri. During the summers of the 1960s and 1970s. a popular entertainment was a river cruise on the party ship the SS Admiral. https://www.builtstlouis.net/admiral01.html
The trips were fun, however, I would always find myself looking at the stones that lined the wharf area knowing that they had been placed most likely by Black slaves.