On St. Patrick's Day, we celebrate all things Irish. We wear green, decorate with shamrocks, attend parades, and throw parties. But why?

Why do we celebrate St. Patrick's Day?

My curiosity to find the origins of the "wearing o' the green" holiday comes because I have a wee bit o' Irish heritage in my family. My grandfather's father was born in Ireland and came to America in 1892 when he was only 18 years old.

While St. Patrick's Day is celebrated in Ireland — and across the world (in Canada, Australia, New Zealand, the United Kingdom, and a few countries in South America) — this holiday is also widely celebrated in the United States, especially in cities like Chicago, New York, and Boston.

Most likely you've heard that they turn the Chicago River green for St. Patrick's Day every year. But rest assured, the dye is allegedly vegetable-based and environmentally safe.

The pressing question?

What really happened centuries ago in Ireland that we still celebrate this Irish holiday on March 17 every year?

Here are 5 key things you need to know about this Irish holiday—and your answers.

1. Who was Saint Patrick?
More than 1,500 years ago, Patrick was born in "Roman Britain" near what is now called Scotland or Wales. He lived from 385 AD — 461 AD. At age 16, Patrick was kidnapped from his homeland, then brought to Ireland by raiders, and taken into slavery.

There, in the mountains of County Antrim, he was made to watch the sheep at night, keeping them from wild animals like foxes, wolves, and bears. Isolated in the cold and desolate countryside, Patrick turned to prayer.

Six years later his prayers were answered, and he escaped.

Patrick returned home. But he often thought about the Irish and prayed for them to convert to faith in God. Patrick became an ordained priest in the Catholic faith (and later a bishop).

He talked about a dream where he would repeatedly hear the "voice of the Irish" calling to him to return to Ireland for them. And so he did.

Patrick went back as a missionary to reach the unreached people of Ireland. He wanted to tell them about the love of God and the Christian faith.

2. When did Americans first celebrate St. Patrick's Day?
St. Patrick's Day — also known as the Feast of Saint Patrick, St. Paddy's Day, or St. Patty's Day — was originally a religious celebration to commemorate Saint Patrick and how he brought Christianity to Ireland.

But the holiday wasn't made official until the early 17th century.

In America, the first celebration of St. Patrick's Day was supposedly in 1737 when wealthy Irish people in Boston threw a party to welcome Irish immigrants who had just arrived.

However, other sources say that Irish Catholics, who had not been treated well upon their arrival on American soil, threw their own huge parties on March 17 to celebrate their heritage.

Today, this holiday has morphed from a religious observation to a mostly secular and cultural celebration.

3. What's the deal with shamrocks?
Legend has it that Saint Patrick used the shamrock (a plant with three broad leaves on one stem) to explain the concept of the Trinity, three divine persons in one God (God the Father, God the Son, Jesus Christ; God the Holy Spirit). And it's become a popular custom to wear shamrocks on St. Patrick's Day.

4. Why do people wear green on St. Patrick's Day?
As for wearing green, some say that green shamrocks and ribbons have been worn on St. Patrick's Day since the 1680s (because of the Irish green harp flag). Others say the color associated with the Irish holiday was originally blue (the color featured on an ancient version of the Irish flag) and then changed to green in 1798, the year of the Irish Rebellion.

But, Irish lore says that long ago they thought wearing green made a person invisible to the likes of leprechauns, the mythical creatures who would pinch anyone they could see (meaning people not wearing green).

5. Why do we celebrate this holiday on March 17?
St. Patrick's Day is celebrated on March 17 because it is the day St. Patrick died (March 17, 461 AD) near Armagh in County Down, Ireland.

A Message of Hope and Victory!
To me, the message of the St. Patrick's Day holiday is one of victory and overcoming obstacles. Despite the hardships Patrick suffered (being kidnapped and taken into slavery), he overcame through the power of prayer and trusting God to deliver him.

So let's celebrate this time-honored tradition on March 17. And believe our great God for deliverance and victory in our own lives!

I arise today…
Christ with me, Christ before me, Christ behind me,
Christ in me, Christ beneath me, Christ above me,
Christ on my right, Christ on my left…
Christ in every eye that sees me, Christ in every ear that hears me.
I arise today.

  -Excerpt from "St. Patrick's Breastplate," a prayer by St. Patrick.