Lars crossed the Atlantic on the ship Monarch of the sea in 1861. He served as the “President” of the 7th Ward on the ship.
In Utah Lars affiliated with the Morrisites but became disaffected with them and, contrary to Morrisite rules, tried to leave the sect in 1862 together with William Jones and John Jensen but the three of them were caught and imprisoned. Later Lars succeeded in escaping and traveled to Salt Lake City to inform the civil authorities that Jones and Jensen were being held against their will. The authorities sent out a posse in an effort to free the prisoners. The “Morrisite War” resulted.
In 1870 "Lewis C. Guertson” and his family were in Salmon, Lemhi, Idaho. At the time of the 1900 Idaho census “Lars Gertson” of Salmon, Idaho reported that he immigrated in 1861.