I think I have found the Halverson family I am looking for sailing on the ship 17de Mai and arriving in New York on June 26, 1849. Are there any other records about these passengers that I can view? At The National Archives website I can order a copy of this Roll #80 for $120 but will it give me any more information?
There may or may not be "more" information on the actual passenger list, but considering the era, probably not. The 5 volume series Norwegian Immigrants to the United States: A Biographical Directory 1825-1850 by Gerhard Naeseth MIGHT contain more information about the family info coming from both Norway and United States.
This is a caveat from one of the earlier posters here at NorwayHeitage about this particular list:
"Reprinted from Budstikken May 1982 with permission of Valdres Samband Notes from the Budstikken: List transcribed by Professor Gerhard B. Naeseth. The first part of the list is composed of passengers from the Bergen area. Further down the list are some from Valdres. The ship’s list has not been easy to decipher. Many such lists have poor handwriting in faded ink. As Historians, journalist and genealogist neither Naeseth nor the Budstikken editors have made any attempt to correct what seem to be obvious errors. As with all genealogical work one must be alert to discover one’s ancestors “hidden” in aliases as they travel to the New World.
Volume 4 of the aforementioned Norwegian Immigrants series has quite a lot of information on the family. That book's take on them says the father's name in Norway was actually Haldor and so the children would be Haldorsen and Haldorsdatter. But in America Haldor used the last name Henderson as did the sons Knut and Claus. Do you still think they are your Halvorson ancestors?