The name 'Toronto' found its way to the current city through its use in the name for the Toronto Carrying-Place Trail (or Toronto Passage), a portage running between Lake Ontario and Georgian Bay, that passed through Lake Toronto, which in turn was used as the name for an early French fort located at the foot of the Toronto Passage, on Lake Ontario. The Severn River, its outlet stream, was once called 'Rivière de Toronto' which flows into Georgian Bay's Severn Sound, then called the 'Baie de Toronto'.
The later French traders referred to it as Lac aux Claies, meaning "Lake of Grids (or Trellises)" in reference to the Huron fishing weirs in the lake.
It was renamed by John Graves Simcoe, the Lieutenant-Governor of Upper Canada, in 1793, not in honour of himself, but in memory of his father. John Simcoe was born on 28 November 1710 in Staindrop, in County Durham, northeast England. Captain Simcoe, an officer in the Royal Navy, died of pneumonia aboard his ship, HMS Pembroke, on 15 May 1759.
The lake is about 30 km long and 25 km wide. Its area is roughly 725 km². It is shaped somewhat like a fist with the index finger and thumb extended. The thumb forms Kempenfelt Bay on the west, the wrist Lake Couchiching to the north, and the extended finger is Cook's Bay on the south. Couchiching was at one time thought of as a third bay of Simcoe, known as the Bristol Channel; however, the narrows between the two bodies of water separate them enough to consider this to be another lake. The narrows, known as "the place where trees grow over the water" was an important fishing point for the First Nations peoples who lived in the area, and the Mohawk term toran-ten eventually gave its name to Toronto by way of the portage route running south from that point, the Toronto Carrying-Place Trail.
Lake Simcoe contains a large island, Georgina, on which there is a First Nations reserve. The lake is dotted with several smaller islands, including Thorah Island (a cottage destination), Strawberry Island (a Basilican retreat), Snake Island, and Fox Island. Pope John Paul II stayed on Strawberry Island for four days just before World Youth Day 2002 in Toronto.
A number of southern Ontario rivers flow, generally north, into the lake, draining 2581 km² of land. From the east, the Talbot River, part of the Trent-Severn Waterway is the most important river draining into Lake Simcoe, connecting the lake with the Kawartha Lakes system and Lake Ontario. From its connection to Lake Couchiching, the Severn River is the only drainage from the lake to Georgian Bay, part of Lake Huron (Simcoe itself is not a Great Lake). The canal locks of the Trent-Severn Waterway make this connection navigable.
The lake is bordered by Simcoe County, Durham Region, and York Region. The city of Barrie is located on Kempenfelt Bay, and Orillia is located at the entrance to Lake Couchiching. The watershed draining into the lake contains a population of roughly half a million people, including the northern portion of the Greater Toronto Area.
The northern shore of the lake contains thousands of cottages and is one of the most popular vacation areas in Ontario.
The Town of Georgina (the northernmost part of York Region, about a one-hour drive from Toronto to the south), lies along the entire south shore of Lake Simcoe and contains smaller residential towns and communities, including Keswick, Sutton, Jackson's Point, Pefferlaw, and Udora among others.
Ecologically, there has been some concern regarding Lake Simcoe. Although it is sometimes known as Canada's ice fishing capital, the lake no longer supports a naturally breeding coldwater fishery. Phosphorus emissions from both urban and rural sources have upset the lake's ecosystem and fostered excessive aquatic plant growth, raising water temperatures, decreasing oxygen levels, and thereby rendering limited breeding grounds inhospitable. Several initiatives, such as the Lake Simcoe Environmental Management Strategy (LSEMS), the Lake Simcoe Conservation Foundation, and the Lake Simcoe Region Conservation Authority, are making efforts to rectify some of the lake's environmental woes. Several towns and communities on the lakeshore depend on Lake Simcoe for their drinking water.
Lake Simcoe is a remnant of a much bigger, prehistoric lake known as Lake Algonquin. This lake's basin also included Lake Huron, Lake Michigan, Lake Superior, Lake Nipigon, and Lake Nipissing. The melting of an ice dam at the close of the last ice age greatly reduced water levels in the region, leaving the lakes of today.
A number of creeks and rivers flow into the lake: