John Leeds was born at Bay Hundred, Talbot County, Maryland. He was the only child of Edward and Ruth (Ball) Leeds, both Quakers. His family was of English origin, his great-grandfather, Timothy Leeds, having come to Virginia in 1607. John's grandfather, William, removed to Maryland about 1648.
John Leeds was probably self-educated and seems to have spent his entire life in Talbot County.
Leeds entered public office in 1734 as one of the commissioners and justices of the peace for Talbot County. In 1738 he became county clerk, an office which he held until 1777, when he either resigned or was removed because he refused to take the oath of allegiance to the new state government. When in 1760 Lord Baltimore signed an agreement with Thomas and Richard Penn providing for a joint commission from Maryland and Pennsylvania to mark off the long-disputed boundary between the two colonies, Governor Sharpe named Leeds as surveyor or "assistant" to the Maryland group. In 1762 he was made a regular member of the commission. Fever and ague contracted while working in the swamps, lack of proper surveying instruments, and the frequent threat of Indian attacks discouraged the commissioners and decided them, in 1763, to employ Mason and Dixon, two professional surveyors, to run the line. They completed the survey in 1767, and the final report of the commission was made the next year. Leeds's account shows that he worked 177 days at a guinea a day.
In the letters of Governor Sharpe to the Proprietor he is always referred to as "the best mathematician in the province. " In June 1769, "having no other instruments but a pocket watch and a reflecting telescope about twenty inches long, of Sterrup's make, " Leeds observed the transit of Venus, obtaining results important enough to be published in the Philosophical Transactions for the Year 1769 (1770) of the Royal Society of London. His article shows that he was a careful reader of that early scientific journal.
From April to October 1766 he served as treasurer of the Eastern Shore, and in October was appointed a justice of the Provincial Court. Partly in recognition of his services on the boundary commission, he was also appointed naval officer of Pocomoke in the same month, and shortly afterward was made surveyor general of Maryland. All of these offices, along with his county clerkship, he appears to have occupied until his Loyalist tendencies forced him out. He was frequently threatened during the Revolution, but was never harmed. Sometime after the war he was again appointed surveyor general and continued in that office until his death in 1790 at Wade's Point. To the end of his life he believed that anarchy would sooner or later follow the separation from England.
Leeds married Rachel, daughter of William and Elizabeth Harrison, February 14, 1726, at the Choptank Meeting House, Tred Avon Parish. They had three daughters, one of them the mother of John Leeds Bozman, the historian.
