Immigrants come to the United States by the thousands each year. Most of the immigrants are legal aliens. They have the papers they need to prove that they want to live in the United States permanently. They want to hold jobs and raise their families. They must apply to the government to get approval to live here. Most immigrants must live in the United States continuously for five years before their citizenship is final. That may seem like a very long time to many people.
While waiting to become official citizens of the United States, immigrants must carry an identification card. The government name for this card is the United States Permanent Resident Card. Most people call it a green card. A green card is a card, but it isn't green. It got its name after World War II. Immigrants had to fill out a form requesting residency in the U.S. The form was printed on green paper. A new form was created in 1977. It is printed on many different colors of paper. It didn't matter. People still call the identification card a green card.
Immigrants seeking citizenship must carry the card in their possession at all times. It must be up to date. Immigrants must be able to show the card to a government immigration officer at any time. In the past, it wasn't very often that immigrants were asked to show their cards. Since September 11, 2001, it has become much more common that aliens are asked to identify themselves.