During the hundred years between 1825 and 1925 many Norwegians left their homes and emigrated to America. The exact numbers may have been between 800 and 900 thousands. Compared with the population size Norway comes second to Ireland in sending emigrants to America.
Tracing immigrant ancestry back to the Norwegian roots is not difficult, but there are some stumbling-blocks. To know what pitfalls there are, a little migration history is necessary knowledge. First of all: The vast majority of the people who left their homes, did it for economic reasons. When an emigration official asked them why they wanted to cross the Atlantic, they usually answered: 'To make a better living.'
The people who went straight from their home farms to the harbors where the emigration ships waited (usually Bergen or Trondheim), doesn't create any great problems for the genealogist. The emigration registers will show where they were born, and give fairly correct names. But quite many men and women who left their homes 'to get a better living' tried other solutions before they chose America.
Most of the Norwegians who emigrated before 1900 were born in Southern Norway. There the population growth made it more and more difficult to get a farm big enough to feed a family. But in Northern Norway there was available land, and most important of all: Very rich fisheries. So, many went north instead of west. As a matter of fact, some historians have named Northern Norway 'poor peoples America'.
To make a living of harvesting the sea is to live with ups and downs in the economy. After 1875 there came a 'down', and many of the people who had come from Southern Norway some years before, now finally decided to try America. But since moving north they could have married, bought a farm - and changed their names a little bit to better suit the regional dialectal naming pattern. A man coming to Northern Norway as Casper Hermundson Tveit could leave for America some years later as Kasberg Hermansen Lien!
There are some special cases I will mention, cases that can make the genealogists hair turn grey. Some of the emigrants, most of them men, had certain reasons to hide their identity: To escape their creditors after a bankruptcy, to avoid paying money for illegitimate children, or to flee from military services. These people can be very difficult to backtrack.
Another group needs some explaining. In cases where a whole family emigrated, the husband often went first to America to get a piece of land. After a while, two or three years, he sent tickets back to his family or money to buy tickets. Some of these men disappeared completely. No money or tickets or even letters came back to Norway. Of course they could have died shortly after the arrival to America, but some of them probably decided to start a new life and eventually acquired a new family.
Many Norwegian sailors signed off their ships in an American harbor, got a job there and never went back to Norway. These sailors, again most of them men, seldom got their names in the emigrant registers. No one knows for sure how big this group is, but as Norway always has had many sailors at sea, it could be numerous.
The last group I will mention, is the people who returned to Norway. Rumors tell that some of them had offsprings 'over there', that was the main reason for coming back. There may be some truth in this for some of the 'returnees'.
What shall the genealogist do when the research halts at any of these 'stumbling-blocks'? The best method is to collect every available piece of information, and let a Norwegian genealogist have a look at the problem.