The 1802 Oxford English Dictionary defined Hamburg steak as salt beef.

NPR: Building a Better Burger

Whatever the origin, Hamburg steak seems to have provided the name, and ground beef became the standard.

NPR: Building a Better Burger

It came ashore with immigrants from Hamburg, who had long since acquired the habit of eating ground beef, raw with onion juice, from nomadic Tatar tribes.

ECONOMIST: As hamburgers go, so goes America?