In 1843, he was ordained a priest, and he responded to Pierre-Jean De Smet's appeal for missionaries to the Native Americans in the Pacific Northwest.
[3] Ravalli traveled with the priests Louis Vercruyesse, Michael Accolti, and John Nobili, Francis Huybrechts, and six sisters of the Congregation of Notre Dame de Namur, arriving at Fort Vancouver, 5 August 1844, after a voyage of eight months.
He brought medical supplies, carpentry tools, and two mill stones to stock the Jesuit missions.
He spent a few months at the mission of St. Paul on the Willamette River (Champoeg, Oregon), where he studied English and ministered to the sick (being skilled in medicine).
In the spring of 1845, he joined Adrian Hoeck at the mission of St. Ignatius among the Kalispel (Pend d'Oreille), on the upper Columbia River in what is now Washington.
In 1854, he assumed charge of the Sacred Heart Mission established by Nicholas Point among the Coeur d'Alenes (Skitswish) of Northern Idaho.
Isaac Stevens, Governor of Washington Territory, who saw it in 1855, said in his official report: "The church was designed by the superior of the mission, Father Ravalli, a man of skill as an architect and, undoubtedly, judging from his well-thumbed books, of various accomplishments."
Near the end of his life, a stroke left him partially paralyzed, but he still visited the sick in a wagon fitted with a cot.