"Baton Rouge, here I come!," actor Noah Wyle says at the start of Sunday's episode of "Who Do You Think You Are?"

Currently starring in TNT's "The Librarians" and most famously on NBC's long-running "ER," Wyle visited the city last year seeking information about his great-great-great-grandfather, John Henry Mills.

The TLC reality series, "Who Do You Think You Are," follows celebrities as they attempt to learn more about their family history.

Growing up, the tale in the Wyle family was that one of their ancestors may have used his wealth to pay someone to serve in his place as a Civil War soldier. Wyle uncovers a much different story, however.

"At the beginning of this journey, I knew I had southern roots, but I had no idea they ran so deep," says Wyle, 45.

After an 1860 census shows Mills was living in Baton Rouge just before the Civil War, Wyle heads for the city, where viewers get a glimpse of the State Capitol before a stop at the Louisiana State Archives. There, Lesley Gordon, a Civil War historian from the University of Alabama, shows Wyle documentation that his ancestor enlisted in the Confederate Army in New Orleans for 90 days in March 1862, and was involved in the Battle of Shiloh (Tennessee) a month later.

"This was a very enlightening visit, like a dream come true for me," the actor tells Gordon.

For further research on Mills, who married Mary Emily Brown in 1863 and settled in Mississippi, Wyle also visits the William F. Winter Archives & History Building in Jackson, Mississippi, and the Jefferson Davis Presidential Library and Museum (Beauvoir) in Biloxi, Mississippi. Details of his great-great-great-grandparents' later years give Wyle much pause.

"You can find whatever you're looking for in your family. You can find a good story, you can find a bad story or you can find a hero, or you can find a villain," he says. "There's just a wonderful complexity when you start shifting through the past."

6 with Schwam

Stephanie Schwam is vice president of programming at Shed Media US and executive producer for 'Who Do You Think You Are?' 

Has working with this show inspired you to search out your own family history?

It has, although the research team here is always so slammed chasing stories for the series that I’ve never been able to ask them for help! I have done a bit of research on my own, which has been fascinating — though short lived — as I come from a long line of eastern European Jews and, frankly, the documents and stories are more challenging to find because of world events and our place in them. I do plan on returning to the search sometime soon.

Do you seek out the celebrities for the series or vice versa?

It’s a combination of both. The network gives us their dream list, and I send out requests from there. We also get a fair amount of folks who come to us because they’re either fans of the show or they have a pal who had a spectacular time. I can’t tell you how many people tell us that the experience of shooting the show changed them forever.

What kind of roadblocks do you encounter on these family history searches?

All kinds! Record loss; entire buildings and/or archives that were burned down or bombed during various wars; countries where record keeping is — shall we say — not a priority.

How long does a typical episode, say the Noah Wyle one, take to shoot, beginning to end?

I think we shot Noah’s in about nine days.

Have there been any cases where once the star found out about their family's history, they didn't want to be on the show?

No. When someone shows interest in being on the show we have a long conversation about where their interests lie, which is a great time for me to find out if anything is off limits. We pride ourselves on not being a “gotcha” show, and we certainly are not out to embarrass anyone or catch them off guard in a negative way. These preemptive conversations are great for us, so we have never had a situation where we shot a story and then the celeb asked us to edit anything out. I know at the beginning of the journey what my limits are. Some people say, “The darker the better! I want to know everything!” Others say that they would love to find a hero in their history if we can.

In the case of Noah Wyle, when was the Baton Rouge portion shot?

Do you know, I can’t remember the month, but it’s was hot as heck and the mosquitoes were vicious!

Follow Judy Bergeron on Twitter, @judybergeronbr.