In the autumn of 1838 as Vicar General, Blanchet arrived in Oregon Country. He arrived at Fort Walla Walla, a Hudson's Bay Company fur trade outpost located in the present state of Washington where he celebrated mass and baptized three Roman Catholic converts. Blanchet’s traveling party included fellow priest Modeste Demers.
Years later, in the aftermath of the death of pioneer Ewing Young, Blanchet was selected to help draft the laws of a new government in Oregon at a February 18 1841, meeting. This meeting was held at David Leslie’s home on French Prairie near Champoeg. The meeting was one of the first Champoeg Meetings that were held to deal with the estate left by Young at his death as there were no known heirs. Two years later these meetings would culminate in the formation of the Provisional Government of Oregon.
He died in 1883 and is interred at St. Paul Cemetery in St. Paul, Oregon.