Copper wire:

After having dug to a depth of 10 feet last year, New York Scientists found traces of copper wire dating back 100 years

and came to the conclusion, that their ancestors already had a
telephone network more than 100 years ago.

Not to be outdone by the New Yorkers, in the weeks that followed, a California archaeologist dug to a depth of 20 feet, and shortly after, a story in the LA Times read: "California archaeologists, finding of 200 year old copper wire, have concluded that their ancestors already had an advanced high-tech communications network a hundred years earlier than the New Yorkers".

One week later. A local newspaper in Missouri reported the following:
"After digging as deep as 30 feet in his pasture near Salem,
Missouri, Old Bill Jadwin a self-taught archaeologist, reported
that he found absolutely nothing. Old Bill Jadwin has therefore
concluded that 300 years ago, Missouri had already gone wireless".