It is thought that meteoric iron was the first iron used. That is, iron that fell from outer space and lay in good shape right on the ground. After such easy sources of iron became scarce, and after techniques to fabricate things of iron were discovered, some of the rich iron ore deposits were mined and the same furnaces converted to smelting ore. This coincides with the rise of Rome.
When did this happen? Probably gradually about 2000 to 500 BC. Both Egyptian and Greek refer to iron in terms that indicate it came out of the sky, so the true iron age would have come after that.
As to the Punxsutawney site: it was probably in use for a long time. The iron smelting could be recent and some of the other artifacts very old. Shouldn't be a problem.