[1] After studying medicine in New York, London and Paris, Dr. Gardiner opened a practice in Boston, where he became a lecturer on anatomy.

But he is most remembered for his purchase and development of over 100,000 acres (400 km2) of wilderness on the Kennebec River in Maine, where he founded what is today the city of Gardiner.

He selected the location of Gardinerstown Plantation, established in 1754 at the head of navigation on the Kennebec River, at its confluence with the Cobbosseecontee Stream, which had falls to provide water power for industry.

[4] In 1774, Dr. Gardiner added his name to a letter addressed to Massachusetts Royal Governor Thomas Hutchinson, affirming his allegiance to the Loyalist cause.

[7] In 1783, Dr. Gardiner spent time in St. John's, Newfoundland, and in 1784 wrote a report enumerating its resources, advocating 11 reasons for settlement.

His second marriage was to Abigail Eppes (née Pickman) sometime prior to his departure from Boston in 1776; she died on November 3, 1780, after they moved to England.