I got this from a book:
"There Was A Fire: Jews, Music and the American Dream" by Ben Sidran
It's about the major contribution of Jews to American popular music. It's a great read.
The American Hamburger got started with Jewish refugees fleeing persecution by the Czar of Russia.
Large numbers of Jews left the "Pale of Settlement" and entered Europe, looking for ship passage to America.
An enterprising Jew in Hamburg, Germany, arranged inexpensive bookings -- the infamous "steerage" class -- but the emigrants had to wait for a ship to become ready to leave.
The potential passengers gathered in one area where they took care of everyone, cooking food and preparing food for the ocean voyage.
Emigrants traveling steerage had to provide their own food for the twelve-day crossing. It needed to be simple to prepare and uncomplicated to serve, strictly kosher, and above all cheap. Kosher meat, being salted, keeps well. When minced, it goes farther than steak. Rolled into balls and flattened into patties, it can be rapidly cooked on a hotplate and served on bread, even on a pitching ship.
The dish soon became known as the Hamburger, after the port of embarcation.
In this way, these Jews brought America’s signature meal with them when they came.