He was born in Providence, Rhode Island and moved to St. Philip's Parish, Savannah, Georgia in 1767 with his brother James, where they bought adjoining plantations.
Martin was active during the American Revolution, serving as a delegate to the provincial congress in July 1775, as well as a member of the local Committee of Safety.
"[2] When Martin began his term as governor, the British held Savannah as part of the southern theater of the American Revolution which, though near an end, was still being fought in Georgia.
Martin wrote to General Anthony Wayne, "Nothing but the present deplorable situation of this country, & the starving condition of the greatest part of the inhabitants, many of whom have not tasted bread kind for more than a month past, could have induced me to trouble your Excellency on this occasion; but impressed with the idea that our distresses, which have been owing to the accumulated horrors of war this country has experienced for this four years past, might entitle us to hope for some small relief for the present from our sister State, has encouraged me to make this application.
With Georgia in a state of financial ruin at the end of the war, he also passed a Confiscation and Banishment Act in 1782 which seized the property of 342 Loyalists identified by name.