Besides providing support for the important fur trade in what is now Manitoba, La Vérendrye wanted to conduct exploration of potential routes for what he believed was an interior western sea.
In 1740 Louis-Joseph had a successful trip exploring the Saskatchewan River to a short distance west of Cedar Lake and mapping the site for the first Fort Paskoya at the west end of Cedar Lake.
On his return toward Lake Winnipeg, he mapped the area and established a site for the first Fort Bourbon.
The map of 1740 indicated a site between the Grand Rapids and Lake Winnipeg, on the northern shore of the Saskatchewan or White River.
In 1741, the elder La Vérendrye sent an expedition of men to establish the fort.