Iver Iverson Immigrant

My great grandfather immigrated from Marteplads, Nes, Buskerud, Norway sometime between 1850 and 1860. He came to America and fought in the Civil War with the Iowa Regulars. He settled in Benson, Minnesota. I am looking for a passenger list and immigrant list showing him as an immigrant from Norway. Any pointers would be appreciated. Thanks. Jan Iverson [email hidden]