There was a MAJOR Irish influx both before and after the civil war. The Italian wave started in the late 1880's and peaked around 1910.
As for Eastern Europe, the largest blast was 1945 to 1955...as "displaced persons" or "DP's" from all of Eastern Europe poured in before Stalin put up the Iron Curtain and wouldn't let people leave.
I went in 1979 to Germany to see the Iron Curtain myself and was very moved.
Before & after WWII, many Serbs, Croats, and Slovieniens came to the US, and many settled around Chicago.
Many Swedes came just before WWI and settled in Northern Illinois and southern Wisconsin as farmers. Around the same time frame, many Finns and Swedes came and settled in Northern Michigan and Minnesota.
Many of this was made possible between 1880 and 1914 by larger steamships (like Titanic) that took immigrants in 3rd class cheaper than ever before.
It's interesting that immigration, in many cases, becomes very localised.
68ROX