While widespread, only two Clovis sites have been excavated in Iowa.

They concluded that the radiocarbon evidence predates Clovis sites in the North American Midwest by at least 1,000 years.

The authors stated that the data required further analysis, and independent analysis of other Clovis sites for verification of this evidence.

Clovis sites dated at 13,500 years ago were discovered in western North America during the 1930s.

The San Pedro Valley has the highest concentration of Clovis sites in North America.

It was the only intact Clovis site ever found in Washington state, and one of many significant prehistoric finds in the state's history.

Jenning's discoveries at Danger Cave were supporting evidence for the Clovis site and the antiquity of humans in the Americas at the time.

These theories are backed by findings in the Monte Verde archaeological site, which predates the Clovis site by thousands of years.

The first report of professional work at the Blackwater Draw Clovis site is in the November 25, 1932 issue of Science News.

Clovis sites mostly date between 11,500 and 11,000 radiocarbon years which means 13,000 years before present at a minimum.