Gadsden was born in 1724 in Charleston, South Carolina. He was the son of Thomas Gadsden, who had served in the Royal Navy before becoming customs collector for the port of Charleston. Christopher was sent to school near Bristol, England. He returned to America in 1740, and served as an apprentice in a counting house in Philadelphia, Pennsylvania. He inherited a large fortune from his parents, who died in 1741. From 1745 to 1746 he served during King George's War as a purser on a British warship. He entered into mercantile ventures, and by 1747 he had earned enough to return to South Carolina and buy back the land his father had sold because he needed the money to pay off debts.