Supposedly they made it to about 2500 Y ago , there was a host of them satill on Wrangle Island and on the Channel Islands in Cal. Thee were the "mini" forms .
There are several hypothesesof why all the mamoths and mastodons went extinct at about the same time but elephas lived on,
Lots of human encampments, including the Clovis site have mamoth bones with cut markes on em. SO maybe humans acquired a taste for em and helped them go extinct .
Another was the rapid post glacial environment changes resulted in a more humid environment and the coastal plain migration ways were inundated by sea level rises so their migration patterns to choice grasslands or pine forests were cutoff,.