Jarvis was born in
Stamford, Connecticut, to Samuel Jarvis, who was the town's clerk, and Martha Seymour. William Jarvis joined
John Graves Simcoe’s
Queen's Rangers in 1777. He was wounded at the
Battle of Spencer's Ordinary in
Virginia in 1781 and was commissioned
cornet in late 1782. At the cessation of the
American Revolutionary War he went on half-pay and attempted to return to Connecticut, however, hostility to the
Loyalists remained strong, and after an encounter with angry
Patriots, fled to
England. In 1791, Simcoe, who had been appointed as the first Lieutenant Governor of
Upper Canada, recommended Jarvis to the Home Secretary,
Henry Dundas, for the positions of Provincial Secretary and Clerk of the Executive Council of the newly established province. Jarvis was instead given the positions of Provincial Secretary and Registrar. Jarvis arrived in Canada with his wife and three children in 1792 and settled in Newark (now
Niagara-on-the-Lake). When Simcoe moved the capital from Newark to
York, Jarvis reluctantly followed. In York, he was granted a town lot and a 100 acre park lot. Jarvis built his home on the town lot, while the park lot was left largely undeveloped. Jarvis was appointed deputy lieutenant of
York County in 1794 and served as a colonel in the
York Militia. He was appointed a
magistrate in 1800, and between 1801 and 1806 served as chairperson of the General Quarter Sessions of the Peace. William and his wife Hannah Jarvis were slave owners who objected to Simcoe's plan to abolish slavery in Upper Canada. In a letter to her father, Hannah incorrectly claimed that Simcoe "has by a piece of chicanery freed all the negroes." One of their slaves, Henry Lewis, escaped and made his way to
Schenectady, New York, where he wrote Jarvis, offering to buy his freedom. ==Personal life==