Winnipegosis continued to flourish as a gathering place for the Cree and Assiniboine tribes, even leading to their request for Pierre De La Verendrye to build a trading post. He built one here in the fall of 1741 on a natural harbor across the river from the existing dock (the Hart farm).
Pierre de La Verendrye, in 1741, sent his son Pierre to establish Fort Dauphin near the mouth of the Mossy River. The father, Pierre, did not himself come to the fort. However he recorded the event by writing to minister Maurepas on May 12, 1742, from Fort La Reine: “I have established a new fort, at the request of the Mountain Crees, on the Lake of the Prairies, the past autumn, named Fort Dauphin.”
Much as been written about Pierre De La Verendrye and establishment of Fort dauphin. In 1749 he detailed the route to follow to reach fort Dauphin from Fort La Reine there is a portage of three leagues to the north east to get into the Lake Of The Prairies (Lake Manitoba). You follow the south shore of the lake till you come to the mouth of a river coming from the great prairies, at the lower end of which is fort dauphin.
Bougainville, in 1757, stated that the Fort Dauphin was situated on the River Minanghnachequeke, or Troubled water. In 1857-890, J.B Tyrrell of the Geological survey, spent the summer in Lake Dauphin and Lake Winnipegosis areas. He noted that the Indians of his time called the Mossy River the Menakweniskegow.
Joseph Derouen (Drouin) placed Fort Dauphin near the place where today is the village of Winnipegosis, and towards the mouth of the River. He wrote in 1760: “route from Lake Winnipeg to Fort La Reine): Dauphin River, 20 leagues, – Partridge Lake, 10 leagues, St Martin River, 3 leagues,- 3 leagues of crossing to the Little Portage of half a league – 10 leagues of lake up to the Big Portage, one league-5 leagues of crossing up to Snake Island, 2 leagues of crossing up to small Snake Island- at three quarters of a league Fort Dauphin: Crees , Assiniboines , Mandans, Whitebeards, Big pikes, little pikes and nations which are in the Prairies.”
J.B. Tyrrell had at first thought that Fort Dauphin was on Lake Dauphin, as he had written in 1892. later he saw ruins of buildings on the bank of the Mossy River, not far from the mouth of the river, and he thought that one of these must have been that of Pierre De La Verendrye.
On the Basis of this information , a cairn was erected in 1952 in Winnipegosis to commemorate the establishment of Fort Dauphin in 1741 by Pierre De La Verendrye.
Though the fort did not remain active for a long period of time, the native community continued to use this area as a gathering place and trading route. Artifacts show they lead full, rich lives due to increasing interaction with the arriving Europeans.
Fort Dauphin on the Mossy River was said to have been abandoned in 1743 for lack of provisions.