African Americans were viewed during the Federalist and Jeffersonian periods of American history. Born in Baltimore County, Maryland, Banneker was the child of a free black father. He had little formal education, but he became literate and read widely. At 21, he built a clock with every part made of wood--it ran for 40 years. After the death of his father, he lived on his father's 100-acre farm, largely secluded from the outside world, with his sisters. Self taught in the fields of astronomy and surveying, he assisted in the survey of the Federal Territory of 1791 and calculated ephemerides and made eclipse projections for Benjamin Banneker's Pennsylvania, Delaware, Maryland and Virginia Almanack and Epheremis, published during the years 1792-1797. He retired from tobacco farming to concentrate wholly upon his studies. He corresponded with Thomas Jefferson and urged Jefferson to work for the abolition of slavery.