Hamilton came to Quebec City sometime before 1807. He and his brother William were merchants importing Madeira wine and selling other goods. In 1809, they set themselves up in the timber trade in Lower Canada, exporting lumber and supplying shipbuilders. As a result of a timber operator being unable to honour his contract, they became owners of a mill at Hawkesbury, Ontario associated with lumbering along the Rideau River. During the War of 1812, George served in the Quebec militia reaching the rank of major. When his brother retired, he moved to Hawkesbury to look after the mill. In 1816, Hamilton became a Justice of the Peace and judge in the new Ottawa District Court of Upper Canada. During the 1820s, a downturn in the timber trade resulted in hard times for the Hamilton family and the business teetered on the edge of bankruptcy.