Around 1825, he started working for the U.S. government as a woodsman, mail carrier, and blacksmith's striker at the St. Peter's Indian Agency next to Fort Snelling.
In 1840, he became a lay preacher for the Methodist Episcopal Church and was considered one of their most successful missionaries to Native Americans in the region.
Stories of his adventures in the wilderness and his encounters with Indians made him a legendary figure in Minnesota history.
During the last decade of his life, he also preached to newly immigrated Swedes who became part of a growing community near his family farm in Afton, Minnesota where he was buried in 1859.
In June 1948, Prince Bertil of Sweden unveiled a plaque in his honor on Kellogg Boulevard in Saint Paul.
It is not a work of art, however, but rather dark and forbidding with a half-circle fringe of whiskers, revealing nothing of the character of the man which was kindly, sincere and devoted.
In Augustus Easton's History of the St. Croix Valley (1909), he is described as follows: Jacob Fahlstrom was a sort of preacher, and he could pray pretty well, and could be depended on upon to do so, providing a good meal was in sight.
The missionaries at Kaposia and Red Rock considered "Father Jacob" as he had now came to be called, such a valuable brand snatched from the burning that his conversion seemed like compensation for their unproductive labors among the Sioux.
Here was one who understood the red men far better than they, one who could be depended upon to carry the Gospel on all his adventurous journeys among the Indians and likewise the white settlements in what is now Washington County.