Starting with the Toronto end, the trail ran up the eastern bank of the Humber River. The trail splits at Woodbridge, with one fork crossing the east branch of the Humber and going up the west side of the river to the vicinity of Kleinberg where it re-crossed the river. This trail was probably used during the seasons when the water was low enough to ford. The other fork stayed on the east side of the river and angled cross-country to King Creek, joining the other fork before crossing the river near Nobelton, some 50km north of Lake Ontario. From there it runs north over the Oak Ridges Moraine to the Holland River, and from there north-east into Lake Simcoe some 80km north.
Once into Lake Simcoe, known as Ouentironk among the First Nations people living in the area, the trail continues north through straights on the north end of the lake into Lake Couchiching. These straights, an important fishing area, gives rise to the name Toronto, as this is "the place where the trees grow over the water". From there the trail follows the Severn River into Georgian Bay. Many of the major First Nations tribes lived in the area around and to the north of Lake Simcoe, which were easily reachable via the many rivers leading to the lake.
A second arm of the trail runs from the Holland River to the south-east, eventually into the Rouge River valley, and from there to Lake Ontario. This arm appears to have been favoured by the French explorers in the area, without ever having seen the Humber. The first European to see the Humber arm was Étienne Brűlé, who travelled it with a group of twelve Huron in 1615.
Further French settlement used the Humber portion of the trail primarily, including the construction of three forts on, or near, the trail. The first of these, Magasin Royale, was built in 1688 about 2km north of Lake Ontario on the Humber near what is today Old Mill. The second, Fort Toronto, was built in 1750 only a few hundred metres north of the lake, right on the trail. The final one, also named Fort Toronto, was built about 2km to the east of the river during 1750 and 1751, and today lies under the bandstand at the Canadian National Exhibition. The trail was widely used by both French and English fur traders until it Toronto started to be permanently settled in the early 1800s, bringing to close its use for over a millennia.