In early 2019, Nicole Clare stumbled upon a dingy old auto repair shop for sale in the Inwood neighborhood at the northern tip of Manhattan. She had been looking for sites to build shelters for a homeless services nonprofit. The auto shop’s lot fit the bill.

Situated next to an elevated train line, the property had seemed ordinary, with a big parking lot and a small building that could easily be razed. By that September, the down payment was in place, and the nonprofit was ready to move forward with design and construction.

But then Ms. Clare received a call about the site’s dark history: Long before the auto shop, before skyscrapers dominated Manhattan’s skyline and even before the subway was built, the site had been a burial ground for enslaved people.

In a city that’s in a constant state of redevelopment, where every block has a past, what is the right thing to do with sites that have a grim back story?

In 1903, as the neighborhood was being developed, workers who were leveling 10th Avenue in Inwood unearthed roughly a dozen skeletons. About 40 percent of New York households had slaves in the early 18th century, and slavery wasn’t abolished in the state until 1827.