Steffenson's of Stavenger Norway

My great grandmother Anna Steffenson came to America in the later 1800's. I have been unable to locate what port she entered the United States. I would love to find the ship manifest that has her name with departure and arrival dates. Does anyone have some advice on how I can find out this info? She passed away many years before I was born and there is no one in our family to ask. My email address is [email hidden].. thanks Connie