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 Bridge corporation, whose seven board members are appointed by the Jefferson County Board of Legislators. Four board members are US citizens and three are Canadian citizens. The Thousand Islands Bridge Authority also maintains and administers Boldt Castle. Tolls are paid only by cash, or with a Commuter Discount Fare Card, which is good for either 16 trips (US$20.00) or 72 trips (US$32.00). No electronic toll collection transponders are currently offered or accepted, although the Bridge Authority has joined the multi-state E-ZPass consortium and was planning to introduce ETC in 2019. The Bridge Authority offers sales of transponders of Florida's SunPass, for