He was born in Evanston, Illinois in 1953 and grew up a Cubs fan. The Cubs of his youth were some of the worst teams imaginable, yet Wrigley Field was always one of his favorite destinations. But he didn't just watch the Cubs there, he also watched the Bears. When he was 9 years old his dad took him to a bar to watch the 1963 Championship game.

"Hey! The game was blacked-out in Chicago," he explained. "We had to watch it somewhere. It's one of my favorite childhood memories."

Though he moved to Idaho in his high school years, and went to Idaho State on a football scholarship, he still followed the Cubs from afar. After graduation, the pull of Chicago was too strong, and he returned to the city of his youth.

He became active in the theater and earned his Actors' Equity card. He performed with the Steppenwolf Theatre Company and was a co-founder of the Remains Theater Ensemble which also included other prominent Chicago actors Gary Cole and Ted Levine. And he attended Cubs games.

But he also knew that if he was really going to make it, he was going to have to travel west.

His big break in the movies came in 1986 in the film "To Live and Die in LA." He continued working in films ("Manhunter," "Young Guns II") and television mini-series like "The Kennedy's" and "Lonesome Dove," but he really hit the jackpot in 2000 with his starring role (he was the producer as well) in the mega-hit TV show "CSI."

But even during those heady days, he longed for Chicago.

"Oh God, I don't know how long I can stick with this," he said. "I'd be in Chicago right now if it wasn't for this show. L.A.'s not my style. Just the other day, I had some friends in from Chicago and we went to see the Cubs beat the Dodgers out here. I was telling them there's no community here. You can't walk across the street from the stadium to the bar. I think that's a microcosm for the whole city."

During the run of the show Petersen still managed to make it back to Chicago once a year or so to sing "Take Me Out to the Ballgame" at Wrigley Field. Then, when he got the chance to walk away from the show, he did it.

And where did he end up? Back in Chicago working in Theater. And back at Wrigley Field.

That's a true-blue Cubs fan.