Thousand Islands – Frontenac Arch is one of four ecoregions of the Mixedwood Plains. The Thousand Islands in the Saint Lawrence River have a distinctive flora and fauna and are a part of the biological corridor. The bedrock is mostly gneiss, granite and marble, more than a billion years old. The Frontenac terrain is the youngest of the Ontario portions of the arch, dated at 1.2 billion years old. These rocks were once part of a large mountain chain of the ancient supercontinent of Rodinia. There is also a meteor crater near Holleford, where the shield meets the limestone plains of southeastern Ontario. The area
Thousand Islands in the mid-1990s with the arrival of zebra mussels, which feed on algae. The water is so clear in some areas that a rocky bottom can be observed in of water. The area has several shipwrecks, and although most of them are over underwater, some are a mere down and can be seen from the surface. Prior to European colonization, the Thousand Islands region was home to, or visited by, members of the Iroquois Confederacy and Ojibwa people. Their name for the islands was "Manitouana" or the "Garden of the Great Spirit". The region was a part of the War