Born at Marlborough Plantation, Colony of Virginia, to emigrant and King's Counsel John Mercer and his wife, the former Catherine Mason (daughter of George Mason II),[1] George received a private education suitable to his class, as he would become the eldest surviving son of wealthy planter and real estate investor.

[4] George Mercer surveyed lands on the frontier, including across the Appalachian Mountains which the Virginia colony claimed according to its charter (which like that of Pennsylvania set no western boundary, unlike that issued to Maryland), particularly those in which his father or the Ohio Company (in which his father and many other Tidewater planters, including George Washington invested) were interested in developing.

The Ohio Company had established one fortified trading post and storehouse at Ridgeley in western Virginia not far across the Potomac River headwaters from Cumberland, Maryland in 1750.

In 1758, the governor assigned both Virginia regiments to regular British Army Brigadier General John Forbes, who planned to march from Philadelphia westward and take Fort Duquesne in the western frontier.

When Mercer arrived in Williamsburg in late October 1765 to attend the General Court, he experienced violent protests as well as condemnation in the Virginia Gazette.

He resigned as tax collector and arranged for the stamps to be kept aboard a royal warship, and his brother James' support prevented physical injury.

His nephew Charles Fenton Mercer possessed many of his papers, and lived the last part of his life with his niece, Judith, and her husband, Rev.

In 1876, antiquarian and attorney William McCullough Darlington (1815–1889) of Pittsburgh, Pennsylvania, bought papers from Jones, and some were published along with the journals of Christopher Gist in 1893.