When Nels and his wife, Karen Catherine Jensen Nelson, embarked for America on the ship John J. Boyd in 1855, they had a one-year-old daughter named Kirstine Marie. Family Tree says that this child died en route and was buried at sea but her name appears on the list of passengers arriving in New York. On the ship manifest the family surname is spelled "Nielsen" and Nels' given name is spelled "Niels." He and his wife crossed the Atlantic with his parents and siblings on the ship John J. Boyd arriving at New York on 15 February 1856. While Soren and the rest of the family continued on to Utah, Nels and Catherine remained in Council Bluffs for about two years while he helped to build handcarts.
Note that her death certificate has an incorrect birth date for her. FamilySearch and the inscription on her gravestone show her birth date as 5 December 1832.