Image by starbeard via Flickr
"On St. Patrick's Day—Tuesday, March 17—millions of people will don green and celebrate the Irish in, and around, them with parades, good cheer, and perhaps a pint of beer".
If you'd like to know more about the saint and the history of the celebration you can go here.
Here is a collection of vintage St. Patrick's Day Greetings Postcards:
All images link to the original sources.