You know you're supposed to wear green and look for leprechauns and maybe eat some corned beef and cabbage. But how knowledgeable are you about St. Patrick's Day? From saintly lore to parade trivia, here are seven little-known facts about March 17.

The story of St. Patrick

St. Patrick wasn't Irish, and he wasn't born in Ireland. He was living in Scotland or Wales (scholars can't agree which) when he was kidnapped at age 16 by Irish raiders and sold as a slave, reports Catholic Online . He spent years in Ireland herding sheep until he escaped. He eventually returned to Ireland where he spread Christianity.

The best (and smallest) parades

There are many parades commemorating the day including New York's St. Patrick's Day Parade, which started in 1762 and now attracts about 200,000 parade participants. By contrast, the first St. Patrick's Day Parade in Dublin, Ireland, wasn't until 1931. The shortest parade is in Hot Springs, Arkansas, where the parade covers all 98 feet of Bridge Street, which was named the shortest street in everyday use by "Ripley's Believe It or Not." Past attractions have included Irish Elvis impersonators, Irish belly dancers, the world's largest leprechaun and Gary Busey.

St. Patrick the exterminator

Legend has it that St. Patrick ran all the snakes (and toads) out of Ireland. Although it doesn't sound very saintly for him to be such an exterminator, it turns out there's not much truth to the tale. Ireland didn't have snakes in the first place, due its glacial history and geographical location. In addition, Ireland has only one species of toad. Technically, St. Patrick chased away symbolic snakes since the slithering creatures often referred to pagan religious practices or beliefs. St. Patrick was famous for converting Irish pagans to Christianity, so that's likely how his reputation as a snake slayer evolved.

green Chicago River on St. Patrick's DayThe Chicago River is dyed a lovely shade of green each year to commemorate St. Patrick's Day. (Photo: Mike Boehmer/Wikimedia Commons)

Green water (on purpose)

Chicago is famous for having the 156-mile Chicago River dyed green each St. Patrick's Day. The practice dates back to 1962 when the Chicago Plumbers Union dumped about 100 pounds of green vegetable dye into the river at the mayor's request. These days, workers use flour sifters to dump an environmentally friendly orange power into the river, according to the Chicago Tribune . The powder (the formula is kept secret) eventually turns the water emerald green, and the color lasts for several days.

No drinking allowed

Drinking beer (green or not) is a big part of celebrating March 17, at least in the United States. Ironically, as recently as the 1970s, pubs in Ireland were legally closed on St. Patrick's Day, because of its national religious holiday status, reports National Geographic.

st patrick in a 13th century manuscript wearing a blue cassockThe earliest known image of Saint Patrick, from a 13th-century manuscript, shows him wearing a blue cassock. (Photo: Huntington Library, Art Collections, and Botanical Gardens)

Green or blue?

Somehow, the "wearin' of the blue" doesn't seem to have the same festive ring to it, but green wasn't the original color linked to this day. King Henry VIII used a gold Irish harp on a blue flag when he declared himself king of Ireland, according to the Smithsonian . Early depictions of St. Patrick also showed him wearing blue garments. But political discord also affected colors and as the people of Ireland distanced themselves from the British crown, green eventually became associated with Ireland (and the country's rebellion).

The shamrock is holy

Now it's on beer glasses and green party hats, but the shamrock got its holiday symbolism as a religious tool. According to some stories, St. Patrick used the three-leaf clover to teach people in Ireland about Christianity. He said the three leaves illustrated the Father, Son and the Holy Spirit of the Holy Trinity.

And speaking of clovers, don't spend your day looking for one with four leaves. There are about 10,000 normal three-leaf clovers for every "lucky" four-leaf one.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.