This is beautiful, as well as illuminating: 200 Years of U.S. Immigration Looks Like the Rings of a Tree
Like countries, trees can be hundreds, even thousands, of years old. Cells grow slowly, and the pattern of growth influences the shape of the trunk. Just as these cells leave an informational mark in the tree, so too do incoming immigrants contribute to the country’s shape.
These immigration “rings” expand during years when certain welcoming factors are prevalent, such as when American immigration policies become less restrictive and its economy offers greater opportunity. The “rings” tend to stay slim during years of war or economic upheaval.
Click the link for the beautiful infographic.