Who, when, and how did knew people come into america?

The Americas were the last (well, second-to-last if you count Antarctica) continents to be inhabited by early humans. Archaeologists estimate that people entered North America by crossing over the Bering Strait, which back then was a wide swath of land, about 15,000 years ago.

People immigrated to America for a variety of reasons, most of which involved seeking personal, religious or economic freedom. The largest reason for immigration, however, was poverty. People left their home countries, where they had low wages and poor living conditions, to go to America and attempt to create a better life for them and their families.

Thats about all I know.
Hope this helps!!