In the struggle for the control of the fur trade geographical advantages lay with the French. They had two excellent routes from Montreal directly into the richest beaver lands of the continent. One of these, by way of the Ottawa and Mattawa rivers, had the drawback of an overland portage, but on the other hand the whole route was reasonably safe from interruption by Iroquois or English attack. The other route, by way of the upper St. Lawrence and the lakes, passed Cataraqui, Niagara, and Detroit on the way to Michilimackinac or to Green Bay. This was an all-water route, save for the short detour around the falls at Niagara, but it had the disadvantage of passing, for a long stretch, within easy reach of Iroquois interference. The French soon realized, however, that this lake route was the main artery of the colony's fur trade and must be kept open at any cost. They accordingly entrenched themselves at all the strategic points along the route. Fort Frontenac at Cataraqui was built in 1674; the fortified post at Detroit, in 1686; the fort at Niagara, in 1678; and the establishments at the Sault Ste. Marie and at Michilimackinac had been constructed even earlier. But these places only marked the main channels through which the trade passed. The real sources of the fur supply were in the great regions now covered by the states of Ohio, Wisconsin, Iowa, and Minnesota. As it became increasingly necessary that the French should gain a firm footing in these territories as well, they proceeded to establish their outposts without delay. The post at Baye des Puants (Green Bay) was established before 1685; then in rapid succession came trading stockades in the very heart of the beaver lands, Fort St. Antoine, Fort St. Nicholas, Fort St. Croix, Fort Perrot, Port St. Louis, and several others. No one can study the map of this western country as it was in 1700 without realizing what a strangle-hold the French had achieved upon all the vital arteries of its trade. The English had no such geographical advantages as the French, nor did they adequately appreciate the importance of being first upon the ground. With the exception of the Hudson after 1664, they controlled no great waterway leading to the interior. And the Hudson with its tributaries tapped only the territories of the Iroquois which were denuded of beaver at an early date. These Iroquois might have rendered great service to the English at Albany by acting as middlemen in gathering the furs from the West. They tried hard, indeed, to assume this rôle, but, as they were practically always at enmity with the western tribes, they never succeeded in turning this possibility to their full emolument.