First Mass4 documented first Masses along this route, mapped in chronological order.
Route
| # | Date | Location | Priest |
|---|---|---|---|
| 1 | July 5, 1840 | La Prairie de la Messe (Green River Rendezvous site, Horse Creek), Wyoming | Fr. Pierre-Jean De Smet |
| 2 | July 10, 1840 | Pierre's Hole (Teton Basin), Idaho | Fr. Pierre-Jean De Smet, S.J. |
| 3 | July 23, 1840 | Henry's Lake, Idaho | Fr. Pierre-Jean De Smet, S.J. |
| 4 | August 1840 | Three Forks, Montana | Fr. Pierre-Jean De Smet, S.J. |