Watching a Weny's commercial, and it made me wonder why we started making beef into patties an then why we put it on a hamburger with vegetables. America is, I'm pretty sure, the #1 consumer of hamburgers. Why did they develop such a popularity here rather than somewhere else?
It was originally called "chopped Hamburg steak" and was style of meat cooked very much like a Salisbury steak. It wasn't until the 1904 World Fair that it became very popular and spread away from German ethnic communities.
Some more history with references:
http://whatscookingamerica.net/History/HamburgerHistory.htm
As a side note, one of my teen year jobs was working at the first McDonald's restaurant in Dublin (on beautiful downtown Grafton Street). The Irish called them "bunburgers" and would pester me with "why are they hamburgers if there is no ham in them?"