The first reason is because the green shamrock leaf is a symbol of Saint Patrick and Ireland. The Irish say a shamrock brings good luck. The third reason is because the people of Ireland would burn green leaves to spread over their land to make their soil richer. There are legends that go along with Saint Patrick's Day. A popular legend is about the leprechaun.
Leprechauns are tiny people dressed in green and they collect pots of gold.
The legend says that if you catch a leprechaun, he will lead you to his pot of gold. The first Saint Patrick's Day celebration in the United States was in 1737. This day is now celebrated all over the world. Some people sing songs and dance to celebrate. The Irish are very thankful on this day because Saint Patrick taught them to read and write.