Evidence from emigration and genealogical records proves the Thompson family traveled to Utah in 1861. The Mormon Immigration Index lists this family under the surname of "Nielsen" in the on the 1861 Monarch of the Sea ship register.
Peter is born as Peder Nielsen son of Niels Christian Thomsen and Maren Jensen in the Lendum Parish Register.
The family came on the ship Monarch of the Sea in 1861. The family consisted of: Peter, father, mother Maren, and children: Cecilia M., Maren, Mouritz Chr., and Niels Andreas.