Found this resource:
https://familysearch.org/learn/wiki/en/Germany_Emigration_and_ImmigrationIt looks like German emigrants left during four main waves (1683-1820, 1820-1871, 1871-1914, and 1914-1945). My paternal ancestors from Germany (and Switzerland and Luxembourg) came to America towards the end of the second wave (mid-1800s) and the beginning of the third wave (late 1800s).
My surname is French, but most of my dad's family is German. The reason? The ancestor that had the surname came from Alsace.
EDIT: I see Franknburger already posted the link I just posted. Oh well.