In “Spider-Man: Homecoming,” Peter Parker’s snarky, woke classmate Michelle (played memorably by Zendaya), refuses to join her academic decathlon teammates on an elevator ride to the top of the Washington Monument, which, as it turns out, spares her from a horrifying situation and a deadly rescue mission for Spider-Man. The reason why didn’t Michelle join them on the doomed elevator ride? Because she didn’t feel like entering a monument built by slaves.

When Michelle’s teacher tried to reassure her that the monument was a slave-free structure, one of the park guides gives a “so-so” gesture, which really is the best response to that question. Looking back, there is no definitive proof that the Washington Monument was built by slaves but, given the state of American infrastructure at the time it was built (in the mid-19th century), it’s safe to infer that slave labor, at least indirectly, played a role in its construction.

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The Washington Monument’s construction, which began in 1848, took four decades thanks to funding problems, control over the project and, of course, the Civil War. The project received donations from dozens of rich benefactors, some of which were plantation owners from the South, making it certain that profits from slave labor went into paying for the Monument.

According to the U.S. Geologic Survey, three quarries supplied the marble that makes up the majority of the Monument: two from Maryland and one from Massachusetts. There’s a clear change in the shading of the marble where material from a different quarry was used, with the upper part of the Monument being supplied in 1879, 14 years after the end of the Civil War and the abolition of slavery. While there are no definitive documents that prove that slaves mined the Maryland marble used in the half of the spire built before the war, it is known that slaves were used in the state at the time.

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But at least some stones in the Monument’s interior came from slave labor. We know this because throughout the spire’s construction, commemorative stones were sent in from state governments and wealthy donors with special inscriptions and designs. According to a study by the National Park Service, 92 of those stones were set into place during pre-Civil War construction, with a number of them coming from states and organizations where slave labor was used for all goods, including mining.

So no, Michelle, there’s no definitive evidence that slaves were hauled to Washington D.C. to build the monument to our nation’s first president — unlike, say, the Capitol or the White House. But in several roundabout ways, their labor certainly played a key role in making it possible.