Many native American peoples occupied the northern edges of South America for centuries. Then, in 1498, this land was visited by Christopher Columbus, on his second voyage to this New World.
As word of his discoveries spread across the European continent, intrepid Dutch and French citizens made the arduous ocean journey to this far away place, and attempted to build settlements at the beginnings of the 16th century. They were hopelessly unprepared for the inhospitable jungle conditions, and many died at the hands of territorial Indians and tropical disease.
"Indigenous perils aside, aggressive exploration continued, as even the English, Portuguese and Spanish ventured in to search for unsubstantiated treasures - never in fact, found here. Regardless, powerful countries continued their efforts to control the area, some by force, others by negotiation, but in the end it was the persistent French who prevailed.
In the mid-1800s, after decades of struggle and thousands of deaths, several French plantations were operating somewhat successfully along the northern coastline, unfortunately on the backs of African slaves. France ended African slavery in the middle of the 19th century, and shortly thereafter, plantation life and all related profits from same collapsed.
Then facing severe prison overcrowding at home, the French government decided to make French Guiana a penal colony, and over time, they shipped many thousands of prisoners to Iles du Salut, and the now infamous Devil's Island.
In 1946, France gave French Guiana Overseas Department status, under which it's effectively an integral part of the French nation; represented in the French national assembly and senate, and governed by a prefect and an elected council.
Today, more than 90% of the population is still concentrated along the coastal areas, adjacent to the cities of Cayenne and Kourou, where incidentally, the European Space Agency has a satellite launch site.