The history of Copper
Copper Plate Reproductions, Spiro Mounds, Oklahoma. Originals made ca AD 1250-1450. Photo of the Spiro Mounds museum display by peggydavis66
this copper plate is from the Spiro Mounds...in Oklahoma.
the population started diving after 1250, due to "exhaustion of resources", or maybe because like Europe they suffered a cold spell/climate change as the Medieval warm period turned into the little ice age.
But there were still quite a few there when De Soto went through...probably his trip spread disease to decimate the remainder, although given the widespread artifacts including those from central American and Mexico, the smallpox and flu might have spread up the trade routes, as it did in the 1750/60 smallpox epidemic.
Note on the Pc twisting of culture. Much of the history of triumphant western culture are being dismatled and replaced with a similarly inaccurate picture of western culture as bad.
Reality check: much of the depopulation of the Americas was accidental, not "genocide": That idea of genocide comes from DeLasCasas Black Legend book documenting atrocities that was used for anti papist propaganda, aka the black legend. (Similar atrocities/depopulation in Ireland was more deliberate are poorly documented and downplayed, since only Papists were killed and they don't count.)
more on the Mississippian copper plates here.
The indigenous cultures of the Americas of course had gold and silver ornaments but not as tools etc. Yet at the time the Spanish came in and wrecked the place they were starting to learn how to harden the copper with arsenic and maybe tin.
the copper at Cahokia came from the Great Lakes region and was soft, but the Incas were learning to harden it with arsenic.
from Wikipedia: Arsenical copper
In South America, arsenical bronze was the predominant alloy in Ecuador and north and central Peru, because of the rich arsenic bearing ores present there. By contrast, the south and central Andes, southern Peru, Bolivia and parts of Argentina, were rich in the tin ore Cassiterite and thus did not use arsenical bronze.
The Sican Culture of north western coastal Peru is famous for its use of arsenical bronze during the period 900 to 1350 AD. Arsenical bronze co-existed with tin bronze for in the Andes, probably due to its greater ductility which meant it could be easily
it also was used in Mesopotamia and in ancient China (spread via trade routes says Wikipedia but the Chinese claim they invented it themselves) but gradually replaced with tin alloys which were easier to work.