What is the latest on Pre-Clovis America?

Answer 1

Here is some of the research being turned out by the George C Frison Institute at the University of Wyoming. It might give you a start on where to look for more information.

http://uwacadweb.uwyo.edu/FRISONINSTITUTE/FRISON/frisonresearchresults.html

Answer 2

This was around 16 thousand years ago around the area of Clovis New Mexico. A knife blade of stone was found and it was named for the area it was found in, one of the oldest found in North America that proves man was here about that time.
Now it's believe man was here far earlier then recently thought. They may have come by a sea route along the Western shore line from the islands of Northern Japan and Russia. The sea was much, much smaller then, probably 600 miles further out then it is now.
Man might just have been here as far back as 20 thousand years ago, we'll have to wait for the proof. They've found artifacts in caves that are as much as 600 feet below sea level in these caves they've found some artifacts from peoples that inhabited them in the past.