What Groups Came During This Time Period? Interestingly, the largest actual number of immigrants were the forced immigrants from Africa, accounting for approximately 40% of the colonial immigrants to the future United States. Based on one of the careful reviews of current demographic studies by immigration historians, the approximate number of immigrants before 1790 came from: Africa 360,000 England 230,000 Ulster 135,000 Germany 103,000 Scotland 48,500 Ireland 8,000 Netherlands 6,000 Wales 4,000 France 3,000 Jews 2,000 Sweden/Finland 500 African-American Colonial Immigration Between 1790 and 1820, between a quarter and a third of a million additional immigrants arrived in the United States, but with a decreasing percentage of African slaves. The vast majority continued to come from Great Britain. However, these different ethnic groups had come at different time periods and had considerably different birth and death rates (African slaves dying the youngest, and leaving the fewest descendants). Therefore, their contribution to America's ethnicity varied greatly throughout the colonies. And if the truth were told, their history is just beginning to be written.