The hamburger seems to be unique that it can be found in both 5-star restaurants and at fast food locations, did it originate as a piece of fine dining that's been brought to the masses or vice versa?

by justhereforhides
Erithom

Take a look at these previous answers which discuss the origins of the hamburger (in the context of "burgers and fries"):

https://www.reddit.com/r/AskHistorians/comments/4mc54u/how_popular_were_burgers_and_fries_before/d3uh6jq/

https://www.reddit.com/r/AskHistorians/comments/39v00a/when_did_french_fries_become_the_standard_side_to/cs72af6/