Benjamin Banneker and the Surveying of the Capital

In February of seventeen ninety-one, a free Black mathematician and astronomer named Benjamin Banneker arrived at the southwest corner of the planned federal territory with a transit instrument, a field notebook, and an assignment from Andrew Ellicott, the chief surveyor commissioned to lay out the District of Columbia. Banneker was fifty-nine years old. He had taught himself advanced mathematics and astronomy from borrowed books. He had built a striking clock entirely from wood, widely considered among the first such clocks built entirely in America, having studied a pocket watch long enough to understand its principles and then rendered them in walnut and cherry.

Banneker's job was to operate the astronomical clock that anchored the survey, the instrument that allowed the surveyors to determine true north and establish the baselines from which every boundary stone and street corner of the new capital would be measured. He worked through the winter months, sleeping during the day and sitting with the telescope through the cold nights, calling out the moment of stellar transit so that Ellicott's crew could check their instruments.

He left the survey by April, apparently to return to spring farm work and finish calculating his almanac ephemeris. Back in Maryland, he completed his first almanac, which he sent to Thomas Jefferson along with a letter that remains one of the most carefully argued antislavery documents of the founding era. Banneker reminded Jefferson that the natural rights Jefferson had declared to be self-evident applied with equal force to people who looked like Benjamin Banneker. Jefferson replied that he hoped Banneker was right. He did not act on the belief.

The boundary stones that Banneker helped place still stand at one-mile intervals around what remains of the original ten-mile diamond. Thirty-six of the original forty stones survive, the oldest federal monuments in the United States.