I recently found this map while reading this post by Meg Miller. She described an amazing interactive map created by the University of Richmond's Digital Scholarship Lab.
Classroom connection: Use a jigsaw activity. Divide the class into two groups. Group A focuses immigration before World War I, and Group B focuses on post-World War I immigration. Have each group look for patterns (number of immigrants, where they originate, where they settle) in the nations they are investigating.