The discovery and dating of Clovis sites across North America established, by mid-century, that people had been present in the Americas for at least 13,000 to 14,000 years.

The Clovis horizon — defined by the distinctive fluted stone points found across a wide area of North America — became the de facto marker of the first Americans in the mainstream archaeological consensus.

But evidence for human presence before Clovis accumulated over subsequent decades, and the strict Clovis-first model eventually gave way to a more open picture in which pre-Clovis presence was increasingly accepted as real and significantly documented.

Sites like Monte Verde in Chile (approximately 14,500 years), Cooper’s Ferry in Idaho (approximately 15,000 years), Paisley Caves in Oregon (approximately 14,200 years), and others contributed to this revised picture.