In Grateful American (Nelson, Feb.), actor Sinise explores his life and career, focusing on his work, through the Gary Sinise Foundation, on behalf of American veterans.

What has been most rewarding about working for veterans?

I don’t feel that I should just support veterans when something really bad happens, like September 11. I know that these people are out there, day in and day out, doing things that none of us know about, trying to chase bad guys down and keep these catastrophic things from happening to our country. If I can do something to show my appreciation for them, that’s the way I feel I can serve and give back—and that, truly, beyond being a good dad and a good husband, gives life purpose and meaning to me.

You write about how popular your Lieutenant Dan character was among veterans. Were you surprised?

Yes, but you can never predict how a role is going to affect someone. Most of the Vietnam veterans we’d seen in films up until then were damaged. At the end, you weren’t sure if they were going to be okay. What was heartwarming, I think, about this Vietnam veteran is that he is doing well at the end. He’s successful in business. He’s married. He’s forgiven himself. He’s made peace with God.

You cofounded the Steppenwolf Theater Company—how does that fit into your story?

When I got out of high school, I was just so passionately obsessed with acting and the theater, but as I describe, not a great student. College didn’t seem like an option. I wanted to keep doing plays, though. I got some kids together, we started doing plays, and named it Steppenwolf. It evolved from productions in the basement of a Catholic school in Highland Park in 1974. We didn’t know if it was going to be a summer project and everybody would leave, and here we are more than 40 years later. It’s pretty crazy—it’s a great American dream story.

What’s next for your foundation?

We’re constantly expanding and changing with our veterans’ needs. Just recently, we had three guys get killed in Afghanistan and three more wounded. We’re trying to provide resources and support for them and their families. In the book, I describe the Snowball Express program—this December, we will take more than 1,000 Gold Star kids, who have lost a mom or a dad in combat or through another tragedy while serving in the military, to Disney World for four days. We’ve done this event for 13 years. It’s pretty great to see these kids healing with each other, enjoying themselves, and saluting their fallen hero.