Eastin was born January 17, 1777, in
Goochland County, Virginia. He was the second son of Augustine Eastin and Mary S. Ford. He married Nancy A Durbin on October 25, 1798. They had eight children: Mary F., Henry J., Louisa A. (Stubblefield), Edward F., Cassandra M. (Rankin), Robert, Thomas and William A.. He died on January 14, 1852, in Henderson, Kentucky. Zachariah Eastin's father, Augustine Eastin, was a Baptist preacher. He was convicted and jailed in
Richmond, Virginia, for preaching to British soldiers. He was threatened with being shot if he persisted. Zachariah was seven when his family moved to
Bourbon County, Kentucky. This was during the time Boonesborough and Bryant's Station were established. In 1792 Augustine participated in a committee that was in charge of enabling Kentucky to separate from Virginia. Augustine and his other committee members,
James Garrard and Ambrose Dudley, reported to the
Elkhorn Baptist Association in favor of forbidding
slavery in the
Kentucky Constitution under development for the new state. Slavery was the major issue discussed at the 1792 drafting convention. Zachariah’s sons, Henry J. Eastin, Robert Eastin, Thomas Eastin, and William A. Eastin all became civil engineers. Henry J Eastin was one of the first engineers to be employed by the State of Kentucky during the period of internal improvements. The other sons constructed other things around Kentucky such as: a saw and grist water mill through the use of a Dam on the Green River, at Spottsville, Kentucky.(5) ==Military service==