Anson Mount is one of the stars of AMC's 'Hell on Wheels.'

Hell on Wheels star Anson Mount still is amazed that a transcontinental railroad ever got built when it did.

"I'm still fascinated by the fact that it was called impossible by just about every engineer on the planet," said Mount, whose series returns for its second season, Sunday, Aug. 12 on AMC.

"And yet it was completed by a group of mostly uneducated men who literally, a month before the project, had been either trying to kill each other or own each other.

"It's an incredible setup for a long-arc television drama. And that gets right down to the greed and the corruption and the racism and the sexism."

Hmmm ... are you sure it isn't set in present day?

Actually, the Alberta-shot Hell on Wheels is set in the 1860s, just after the U.S. Civil War, as the Union Pacific Railroad continues its westward construction.

Mount, who plays lead character Cullen Bohannon, said that while the first season was focused largely on plot, the second season, as often is the case, becomes more about the characters.

"Just like you find out in the second season forward in Breaking Bad (another AMC show), it's a show about ego," Mount said. "You can't do a show about cooking crystal meth for six seasons, it just doesn't work. It's about ego.

"In the same way, this show (Hell on Wheels) is about ambition."

Characters and ambition intersect in the second season of Hell on Wheels, with the relationship between Cullen Bohannon and Elam Ferguson, played by Common, emerging as one of the most intriguing.

"Common and myself and the writers were all very definite at the beginning that we were not going to allow this to become Richard Pryor and Gene Wilder, 'The black guy and the white guy are going to be buddies, and everybody's going to love each other,' " Mount said.

"We wanted it to be very true to the tropes and the stereotypes and the conflicts at that time, particularly between a former slave and a former Confederate."

Mount was asked how long he'd like to see Hell on Wheels run.

"Well, I've thrown out there that I wouldn't mind six (seasons)," Mount said. "When you add together all the outlying projects that had to be completed once the rails were connected, it was a six-year engagement.

"We haven't even started drilling through the Rockies, which is a huge part of the story."