In 2004, I made a map of the United States out of pennies. It was sitting loose on the kitchen table - no glue or anything else holding it together. I took a few pictures, showed it to friends, left it there for about a month. Then I put the pennies back into jars.
It's 14,238 pennies. Roughly 4' by 2'6".
I sorted the pennies by color to outline the states.
Close-up of Wisconsin.
The Original was 9 pennies thick. If it's just one or two layers, adding the next penny, or bumping the table, makes the rest of them move. Stacking them up gives it some heft and stability.