Benjamin Banneker was born in 1731 near Baltimore. His grandmother, an Englishwoman, taught him to read and write. For several winters he attended a small school open to blacks and whites. There he developed a keen interest in mathematics and science. Later, while working as a farmer, Banneker continued his studies in mathematics and taught himself astronomy. In 1753 he completed a remarkable clock. He built it entirely of wood, carving each gear by hand. His only designs were a pocket watch and an old photo of a watch. The watch has kept near perfect time for more than fifty years. In 1791, Banneker served as assistant to Major Andrew Ellicott, the surveyor appointed by President George Washington