Benjamin Banneker was already a practiced mathematician and astronomer when he was approached in February 1791 by his friend Andrew Ellicott to survey the land staked out for the new United States capital. A free black who grew up in Maryland as a farmer, Banneker was more than a laborer. Though his formal education ended at an early age, he continued to study science and physics and would later write a series of best-selling almanacs. He designed and built a striking clock at age 22 that kept perfect time for forty years until it was destroyed in a fire. But, perhaps him most long lasting mark was the unique role he played in the development of the nation's capital — a job that went far beyond what Ellicott orginally had in mind.