The origins.

Northern AMerica was inhabited as early as in 10,000 BC by NAtive Americans( called Indians).
The first Europeans who set foot on the continent were the vikings around 1,000 AD. But it is mainly Christofer Columbus who is acknowledged as the discoverer of the continent in 1492. This discovery is at the origin of numerous European settlements.
The first british town ever founded in North America is Jamestown, Virginia(1607). IN 1620, the pilgrim Fathers who escaped Britain on board the MAyflower in order find religious in this Promised LAnd, founded the the town of Plumouth virginia.
One year later with the local native Americans they celebraded their survival thanking god for enabling to survive: it was the first THANKSGIVING.

A nation of immigrants.

The USA has always attracted immigrants, who were search of political and religious freedoom as well as economic opportunities.
The famine in Ireland in 1840 and industrialisation were a important causes for emigrting.
To control the overflow of immigrants, the Americans set up immigration centres as Ellis Island, which was open from 1892 to 1954, but in the 20th century the USA voted new laws to restrict immigration.
Now a green card is necesary live in America.