St Patrick's Day marks the Roman Catholic feast day for Ireland's patron saint who died in the 5th century. St. Patrick (Patricius in Latin) was not born in Ireland, but in Britian.
Many myths surround St. Patrick. One of the best known – and most inaccurate – is that Patrick drove all the snakes from Ireland into the Irish Sea, where the serpents drowned, but snakes have never been native to the Emerald Isle.
In the US, it's customary to wear green on St. Patrick's Day. However, in Ireland, the color was long considered to be unlucky.
Colonial New York City hosted the first official St. Patrick's Day parade in 1762, when Irish immigrants in the British colonial army marched down city streets. In subsequent years, Irish fraternal organizations also help processions to St. Patrick's Cathedral. The various groups merged sometime around 1850 to form a single, grand parade.
Today, New York's St. Patrick's Day parade is the longest running civilian parade in the world. This year nearly 3 (aff) million spectators are expected to watch and around 150,000 participants plan to march.