[1] After several assignments in Quebec, Langlois joined Jean-Baptiste Bolduc on a journey to the Pacific Northwest to aid Catholic conversion efforts there.
Greeted by fellow Catholic Louis Désiré Maigret, he informed the two priests that they had to wait several days for the next ship to visit Honolulu, the Hudson's Bay Company barge Cowlitz.
[4] Disembarking at Fort George on 19 September, the Catholics met priests from the Methodist Mission departing the region for the United States of America.
While in the Boomtown of San Francisco, Father Jean Baptiste Brouillet convinced Langlois to remain there to administer the spiritual needs of the California Gold Rush city.
[7] Bishop Joseph Alemany of the Diocese of Monterey appointed Langlois as vicar of the northern half of the spiritual district.