(tco 3) in the early 19th century, the largest source of european immigration came from

The correct answer is - Ireland.

Most of European immigrants in the early 19th century came from the island country of Ireland. This was due to the infamous ''potato famine'' that took place in Ireland, when a very large population died because of starvation, and most of the people in the country were on the verge of survival because the main food source, the potato, was mostly destroyed by a disease. The US, even though it had strict migration policy at the time, came forward and allowed the Irish people to move in the country, which was a very humane act.