Banneker was the son and grandson of freed slaves from Africa. His mother and grandmother were indentured servants from England who freed, and then married, their male slaves. The original family name was Banna Ka, or Bannakay. His father, Robert Bannakay, was notable for having built a series of dams and watercourses that successfully irrigated the family farm where Bannaker lived most of his life. Banneker was taught to read and do simple arithmetic by his grandmother and by a Quaker schoolmaster, who changed his name to Banneker.
At age 21, Banneker's life was changed when he saw a neighbor's patent pocket watch. He borrowed the watch, took it apart to draw all its pieces, then reassembled it and returned it running to its owner. Bannaker then carved large-scale wooden replicas of each piece, calculating the gear assemblies himself, and used the parts to make the first striking clock ever built in America. The clock continued to work, striking each hour, for more than 40 years. This event provided the impetus to turn him from farming to watchmaking.
His work led him to the study of astronomy at age 58 and he made the calculations to predict solar and lunar eclipses and to compile an ephemeris for his Benjamin Banneker's Almanac, which he published from 1792 through 1797. He became known as the Sable Astronomer.
In 1791, he was hired to assist Pierre L'Enfant[?] in surveying the Federal District. When L'Enfant was dismissed after numerous blowups, he took his drawings with him, but Banneker was able to recreate them from memory, thus preserving the famous plan of Washington, D.C..
Banneker's intellectual achievements convinced many Americans, among them Thomas Jefferson, that African-Americans were not intellectually inferior to whites.
In 1980, the U.S. Postal Service issued a postage stamp in his honor.