The oldest site we know if is the Jim Pitts site, which was located about 20 miles west of Custer, in the Black Hills. The earliest inhabitants of the site have been identified as belonging to the Goshen complex, and it has been dated by radiocarbon to about 11,300 years ago. Note that this is the oldest site we know of now . We do not really know when the first people came to the Americas. Until recently, it had been commonly believed by many North American archaeologists that people could not have arrived via the Bering Straits before about 12,000 years ago, when the great ice-age glaciers retreated.
Radiocarbon dating is perhaps the most common way to date sites.
This measures the proportion of carbon isotopes in a charcoal sample to provide an estimate of time since the carbon was part of a living being. Archaeologists can also date sites by the style of the stone, bone, and pottery artifacts found at them. Sites are found by walking the landscape and keeping a sharp eye out for the telltale signs of past human use. Only if you want us to. Artifacts from public land are the property of the state or federal government and cannot be collected or excavated without a valid permit.