There were 3,347 registered runners in the 2012 5K on St. Patrick's Day race in downtown Colorado Springs

For nearly three decades, John and Carol O'Donnell have shaped St. Paddy's Day in the Pikes Peak Region. It has become a celebration of running and cycling.

On March 11, they'll host the 33rd 5K on St. Patrick's Day, an event they started in 1985, and the second Pedaling for St. Pat's 50K Bike Ride. And they've added the Colorado Springs St. Patrick's Day Sports Expo, March 11 at the Pikes Peak Center..

The run has grown to become one of the biggest races in the state, with more than 3,000 runners rolling like a green tide down Tejon St.

"We were the race of the month in Runners' World and Colorado Runner Magazine's 5K of the year in 2011," said John O'Donnell, a Colorado Springs native and 1971 St. Mary's High School graduate (Carol graduated from St. Mary's in 1975.)

And participation has exploded in recent years. In 2010, there were 1,666 finishers. In 2011, that number climbed to 2,139, then burst to 3,091 in 2012. Officially, 3,347 registered in 2013.

How does that happen? Good weather and racing on a holiday weekend helps. But there is more to it. O'Donnell loves running. He was a football player and track man at the University of Southern Colorado (now CSU-Pueblo). And he loves to talk about placing third in his age group on Pikes Peak, "but that was 44 years and 80 pounds ago," he said.

And the O'Donnell's bring experience to the tough game of event organizing.

"That's what we do," O'Donnell said. "We've produced over 100 races, parades, air shows, bike rides, festivals and welcome-home events."

The St. Patrick's day run - which for years was held in Old Colorado City - was always popular.

In 1985, O'Donnell included an invitation-only mile race on Colorado Ave. The winning time was a blazing 3 minutes, 54.9 seconds by John Lohman.

The 5K, now contested on the downtown streets of Colorado Springs, still draws some of the top runners in the state. In 2010, Kenyan-born Robert Cheseret won in 15:00. In 2011, former Olympic steeple chase runner Justin Chaston won the event. Last year, the Boulder Running Company's Tommy Neal took the win.

"We had a great field of runners, tons of people and you couldn't ask for a better day," Neal said as he caught his breath at the finish line.

The O'Donnell's also produce the St. Patrick's Day Parade, which follows the run.

But the big addition - the one that has caught the ear of Front Range cyclists - is the new Pedaling for St. Pat's 50K Bike Ride. In it's inaugural year, the ride drew nearly 500 riders. O'Donnell was expecting about 200.

"I think the technical term for that is 'pleased as punch,'" said Sally Davis, public relations coordinator at O'Donnell and O'Donnell.

Sue Blumberg, a former said City of Colorado Springs administrator approached O'Donnell with the idea of a bike ride.

"They wanted us to have something that would draw people from around the state," he said.

This year, the O'Donnell's are reaching to gather riders from Wyoming to New Mexico. The ride is being billed as the kickoff for Colorado's 2013 cycling events. Part of the pre-race buildup includes TV spot with Colorado Gov. John Hickenlooper inviting cyclist to participate.