ships from Norway to USA approx.1876

I am looking for the ship my Grandpa: RASMUS TONSETH;perhaps spelt; TENSETH or TONSET came to the USA on from Norway. I have no idea where the ship letf at. He may have been with two(2)brothers;one named OLE. Also a sister. Rasmus was born October 10 1863 in ROMSDAL(RHOMSDATHLEN)Valley. I was told he left Norway in 1876. Appreciate any information on this family. THANK YOU!! Juanita Smith(State of Iowa USA))