The tradition started in 1970 when one of the McArdle children painted a tiny shamrock on a downtown curb to honor their family's Irish heritage.
Forty years later, the McArdle family continues to head downtown right around St. Patrick's Day to give the shamrock, which is at the intersection of South Stone Avenue and West Pennington Street, a fresh coat of paint.
Andrew McArdle painted the first shamrock downtown in the early hours of March 17, 1970, so their mother, Ann, would see it on her way to work at the Mountain Bell Telephone Co.
"She saw it and just loved it," said Victoria McDaniel, one of Ann's children. "It became a tradition."
McDaniel's parents, John and Ann McArdle, moved with their five children from a Boston community rich in Irish culture to Tucson in 1969 so John could get some relief from his rheumatoid arthritis.
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"They taught us so much about culture, tradition and heritage," McDaniel said of her parents, who have both died. "We all developed a respect for diverse cultures and traditions. It means a lot to us."
All five of the McArdle siblings pitched in to paint a giant shamrock at the downtown intersection in 1971 and over the years their own children, grandchildren and close friends have joined them.
Family and friends celebrate and dine on corned beef and cabbage, potatoes, carrots and Irish bread before they go downtown to paint the shamrock.
This year's party marked the 40th anniversary of the first shamrock, but it also featured a wedding.
McDaniel's daughter, Brianna, married Mitchell Davis on Friday and after the party, the family went to work painting the shamrock.
"We thought of it as the only way to begin our lives together," Brianna said before the wedding.
The couple live in Oceanside, Calif. and visit often in March to take part in the family tradition.
Today will be the 10th year the family enters a float in the Tucson St. Patrick's Day Parade.
"It's crazy and it's hectic and chaotic, but it's the younger generation coming together to honor our parents and grandparents," Brianna said. "I don't know any other family like ours. I've always felt so blessed to be a part of us."
if you go
• What: Tucson St. Patrick's Day Parade and Festival featuring Irish music, dancers, games, food and more.
• When: 10 a.m. to 5 p.m. today. The parade starts at 11 a.m.
• Where: Armory Park, 220 S. Sixth Ave. The parade begins at 14th Street and Stone Avenue, goes north to Broadway, east to Sixth Avenue and south to Armory Park.
• Cost: Free
Contact reporter Andrea Rivera at email@example.com or 807-8430.