There is a real sense in which the Royall House and Slave Quarters museum is a memorial to the people enslaved there and in particular, in terms of "tripping over a branch and finding it's bone," there is a stumble stone on the sidewalk in front of the house, in memory of one of the enslaved residents. (based on the Holocaust ones in Germany https://en.wikipedia.org/wiki/Stolperstein)
Phillis Wheatley is one of those in the Boston Women's Memorial.
https://www.boston.gov/departments/womens-advancement/boston-womens-memorial
I had remembered seeing a statue of Elizabeth Freeman (MumBet), but it's not in New England, even though she was in Massachusetts when she became famous for her lawsuit to become free. The statue is in DC, at the NMAAH. And there's the about to be removed statue at Park Square of Lincoln standing over chained people, which is supposed to commemorate Emancipation.
Of course all the Viking things are white-supremacy based, although it might not have been articulated exactly that way in the past.