This stretch of the highway follows the shoreline of Lake Huron over Canadian Shield that was scraped off by the Ice Age glaciers, that covered the area until 10,000 years ago. As they receded, meltwater collected in the Nippising Great Lake, larger than any of the current Great Lakes. Much of the meltwater contained fine milky sedimentary rock flour (like the rivers and lakes of the Rockies today). As the glaciers receded, land rebounded upward form the weight no longer pushing down on the earth's crust.
The waters flowed eastward over what is now the French River to Lake Nippising, then the Mattawa River down to the Ottawa, and down the Ottawa to the Atlantic (though for a while, it was detoured south from Montreal via Lake Champlain and the Hudson River.) The rock flour have accumulated into today's clay deposits, with coarse sands and rocks strewn atop the clays in valley bottoms.
After the glaciers receded vegetation was quick to take root and grow, including mosses, lichens and spruces. The large islands of limestone deposits in this area created a variety of growing and soil conditions.
During the Great Depression, federally funded relief projects allowed thousands of men to be hired to construct highways in remote areas of the province from temporary camps (named "Bennett Camps" after the Prime Minister, R. B. Bennett). Beginning in 1931, certain routes were designated as the Trans-Canada Highway, including the route between Sault Ste. Marie and the Quebec boundary as well as the planned connection to Thunder Bay and Winnipeg. At the time, there were no roads between Thunder Bay and Sault Ste Marie, only rail lines and a ferry connection.
By 1937, the highway from Sault Ste. Marie to the Quebec boundary was 1,045.8 km (649.8 mi) long. Portions were paved at this point: east of Sault Ste. Marie, west of Blind River, through Sudbury, east of Sturgeon Falls, through Mattawa, and from Chalk River to Quebec; the remainder was a gravel road.
This was once a key fur trading fort with connections west to Lake Superior and south to Lake Michigan. Some of the oldest land titles in Sault Ste Marie are held not in Toronto, but in Quebec City, and were signed by Samuel de Champlain the first governor of New France form 1632-1635.
The first industry here was a pulp mill, built in 1896 to harvest and process the vast timber lands in the area. The St Mary's River became important for shipping when iron was found near Wawa, and the rapids here were dammed in 1918 for hydropower production. Canada built a canal to bypass the rapids at Sault Ste Marie (the rapids of Ste Marie), in 1895, the new country still paranoid about having naval power access the upper great lakes, from the experiences of the War of 1812. The construction of the power dam required a canal for shipping to bypass the power dam.
Today, most shipping uses the locks on the American side, which can handle ships with widths (beams, in shipping parlance) of up to 105 feet, twice as wide as the older Canadian locks, now a national heritage site.
The dam, built under the International Bridge not only assists navigation of the St Lawrence Seaway, but also controls the release of water from Lake Superior to Lakes Huron and Michigan, where there are many properties guilt along their shorelines that could be affected by uncontrolled flooding. At Bellevue park, 4 km to the east of the dam is a great spot for wildlife and waterfowl viewing.
The buildings in Sault Ste Marie are built from Jacobville Sandstone, the youngest rock in the Canadian Shield, and found in plentiful and practical quantity in an outcrop around the rapids
The highway in and around Sault Ste Marie lies on one of the several terraces of slit & clay left behind as the glaciers were receding and before the lake of meltwater drained into the Atlantic
The Garden River Reserve has its own sawmill and is reforesting a mix of jack pine, red pine, white pine, white spruce, and balsam poplar.
In recent years, the old Highway 17 running along the St Mary's River through the populated reserve areas, as well as through the community of Echo Bay, has been bypassed by a faster 4-lane road around them, speeding traffic and improving safety. From time to time the First Nation has blockaded the highway as a political protest.
In 1970, St. Joseph Island Bridge near Sault Ste. Marie opened, making this island accessible without a ferry ride. Highway 548 connects from the Trans-Canada Highway 17, and takes visitors around the perimeter of this scenic island. Richards Landing is popular jumping off point for those sailing the North Channel, above Manitoulin island. St. Joseph Island is a popular detour during the fall season, for its eye-popping diversity of coloured foliage.
Just west of Richards Landing is Sailors Encampment, which is a prime ship-watching spot, where you can catch passing Seaway traffic. At the extreme south end of the island is Fort St Joseph, a National Historic Site, which was built in 1796 to protect fur trading. This was the base for the first British assault on American territory in 1812, during the War of 1812, though the Americans got their revenge destroying the fort in 1814.
2 km east of this turnoff and 2 km west of Desbarats River is a rock cut showing sand deposited in ripples, which have been fossilized some 2.5 billion years ago.
This town was the location of the first mine in the Canadian Shield, which extracted copper from 1846 to 1876.
The area between Bruce Mines and Blind River (roughly 75 km) has clay deposits and attracted farmers, though the quality soils were spotty at best.
Thessalon is a port at the mouth of the Thessalon River on Lake Huron. Fishing on the lake was a strong industry, operating out of the ports of Thessalon and Blind River, but this has been adversely affected by lamprey in the 1950s.
About 10 km east of the community is a rise in the land which has exposed massive sand and gravel deposits, useful for the construction of the Trans-Canada Highway, and many other projects
The mouth of the Mississagi River, which was a major artery in to the timber lands north of Lake Huron. Today, this river has four hydroelectric power dams, which generate a half-million kilowatts.
The town also had one pf the largest timeber operations in North America, which peaked in 1929 when a million logs were cut.
East of Blind River is the Murray Fault, which occurred about two and an half billion years ago.
In 2018, two bridge replacements are scheduled: River aux Sables Bridges and Cameron Creek Bridge, north of Hwy 17 at Massey.
Uranium was found at the Pronto Mine back in the 1950s, and the mine entrance is visible form the highway. The uranium is found in a conglomerate of quartz pebbles that date back two and an half billion years. 24 kilometres up highway 108 is Elliot Lake, a well laid-out town. The Mining and Nuclear Museum here chronicles the geology, the mining and energy industries, as well as local wildlife.
When you cross the Serpent River, you will notice the azure blue colour of the waters. The mouth of the Serpent River on Aird Bay is beside the Serpent River campground, west of the Highway 108 turnoff. The Serpent River bridge is to the east of the turnoff, and the Serpent River First Nation community is along Lake Huron shore east of that. The First Nation lands include everything south of the river west of this point on the Trans-Canada, as well as the land south of the Espanola River, further to the east. The Serpent River Reserve operates its own sawmill.
At the mouth of the Serpent River, you may notice a yellowish crust on rocks. This is a result of an acid plant built there, to serviced the uranium industry in Elliot Lake. The plant has long been closed, and the area has been tidied up, but this is still left.
9 km east of Serpent River, east of Walford, you will see sand dune like formations along the highway, accumulated from the glacial rivers in this area.
Just west of Massey the highway passes through a group of island-like rock outcrops, that were actual islands when Lake Huron was much higher after the glaciers were beginning to recede. When the lake fell, these rock outcrops were left surrounded by a lake bottom of clay, silt, and sand.
East of Massey, the influence of Lake Huron disappears, as the highway moved upland and inland. The area's hills are covered with hardy white pine, though even they thin out east of Espanola/McKerrow
The rail line at this point connects Sudbury with the Great Lakes, and their coal resources. It also links to quartzite flux, necessary for smelting, that was found in the LaCloche Mountains in this area. The LaCloche Mountains are estimated to be over 3.5 billion years old, and are one of the oldest mountain ranges on Earth. Believed to have once been higher than today's Rocky Mountains, they remain among the highest altitudes in Ontario. Killarney Provincial Park is located in the range and is very popular among tourists, who also like the "Heaven's Gate Trail", along the length of the range from Willisville to Massey.
The Spanish River was one of the first northern rivers to become industrialized, with a pulp mill built here in 1905, with hydroelectric dams further up the river.
Manitoulin Island, has an area of 1588 square miles, and is the world's largest freshwater island (in other words, the largest island in a lake, on a continent), but its Maintou Lake is also the largest lake on an island in a lake in the world. This island has very little glacial debris and has very little arable land suitable for cultivation. The rugged land, especially between Espanola and Little Current was a favourite of the Group of Seven painters. On the island, South Baymouth is the dock for a ferry that connects to Tobermory on the Bruce Peninsula, and some of the world's best scuba diving at Fathom Five National Park.
Manitoulin Island Detour
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