Source: Library of Congress
Technically, the very first European immigrants in North America were the Norsemen, who made an effort to settle in Newfoundland (Canada) around 1000 AD. Thorfinn and his wife gave birth to Gudrid who is supposedly the first European baby born in North America.
The great emigration from Norway to America however began in the year 1825 with the first organized sailing from Stavanger to New York with 52 persons aboard the Restauration. The journey took three months and 4 days. The passengers were mainly Quakers and the majority settled in Kendall in New York State.
From the time the first settlers arrived in North America in 1825 to 1925 a total of 800,000 Norwegians left their home country for the New World. That means that about one third of the Norwegian population immigrated to the United States during that period, a smaller number stayed in the Canadian territory. The number is only exceeded by the Irish immigrants where a higher percentage of its population arrived in the USA.