From Norway to U.S. before 1850

After studying the immigration paths prior to 1850, it appears that a common route was from Norway directly or through other ports to Canada. After that was some rail and the ships to Milwaukee, Chicago and other midwest destinations in the U.S. I would guess he emigrated between 1840 and 1849 (Wisconsin resident in July, 1850). The passenger lists do not seem to be available for many ships for many reasons. I know my great great grandfather (Peder) was near Milwaukee (50 miles away) in July, 1850. His first name was Peter/Peder (b. 1814-1817 likely) and his last name in the U.S. (Ondell) was probably an Americanized version of Aandal, Aandahl, Uldalen, etc., and he was probably (80% chance) from the coast or inland south of Kristiansund. I have found several possibilities, but have not been able to eliminate or include them after looking at Norwegian census records (1865) and the available on-line Norwegian emmigration records. The area Peder lived in1850 was very primitive and the first church was established in about 1841, when the first white female was born in the county. Peder/Peter later married in 1851, but it seems unlikely this was his first wife at the age 37. He also married again in 1869 and this women was recognized as the acting "mother" of his 4 children (born 1851-1857). the U.S. records are not as accurate as the Norwegian records since they were taken by volunteers that were first or second generation immigrants from other countries. In addition, they did not ask the birth date, but asked the age, which required a calculation based on a memory or a story to create a birth date. I would like to research whatever records are available (on line or in person) to look at the possibilities. At a recent monthly lunch of the Norske Torske Klubben in St. Paul, Minnesota I was advised to look at all the possibilities through Canada, but have a little idea of where to go beyond the limited digital databases. - The meeting was great - 350 Norwegians singing the Norwegian national anthem as loud as they could!!!. I am willing to go to Quebec or eastern Ontario since it is only less than 1000 miles IF I have a chance to end my 15 year search. I know he was born in Norway and know he was in Wisconsin in 1850. Before that, I have no knowledge of any specific ancestors or family. Thank you for any assistance and suggestions. Dick