As a TV and film actor, William Mark McCullough aims to always keep “moving forward and upward.” The Mercer University alumnus said he has been fortunate to see his career climb a little each year, and one of his biggest projects to date is a blockbuster in theaters right now.
McCullough plays Commander Dennis Dunphy in Captain America: Brave New World, the latest film from Marvel Studios.
The Savannah native discovered a passion for acting at Mercer and earned a bachelor’s degree in theater and political theory. He went on to earn a Juris Doctor degree from American University and worked in politics and law in Washington, D.C., before he decided to pursue an acting career.
“The reason I became an actor is because I had to take an art elective at Mercer, and I took acting. I think there’s something wonderful about liberal arts education. It kind of forces you to look into parts of the world that you may not have otherwise,” he said. “Had I not taken that acting class at Mercer initially, never would I have become an actor because that desire and love and joy wouldn’t have been sparked the way it was by walking into that class that first quarter.”
McCullough’s movie credits include American Made with Tom Cruise, Logan Lucky with Channing Tatum, Arsenal with Nicolas Cage and John Cusack, and Hillbilly Elegy with Glenn Close and Amy Adams.
He has appeared on numerous TV shows, including Sweet Magnolias, The Unseen, The Resident, The Walking Dead, L.A.’s Finest, Saints and Sinners, Living the Dream, Mercy Street and Underground. One of his most recent television roles was as Boston Corbett — the man who killed John Wilkes Booth, who assassinated President Abraham Lincoln — in 2024’s Manhunt.
In the new Captain America, he plays a Navy SEAL commander and makes his on-screen debut about 10 minutes into the film.
To prevent plot details from leaking, Marvel stays tight-lipped when it comes to auditions and filming, McCullough said. When he auditioned, he only knew it was a Marvel project but not which specific one. He was given a vague description of the character and was asked to perform a made-up scene.
Even after landing the role, McCullough didn’t receive any more details until the day before he started filming in Atlanta. He was given the script for only his scenes — which he had to access through a secure website and couldn’t print — and saw that he had dialogue with Captain America. It wasn’t until much later that he learned more about his character and his connection with the comics.
“They were really serious about keeping things under wraps, which I totally get,” he said. “But it was really fun. It was really exciting. It was challenging just in the fact that I didn’t have a lot of information to go off of and had to kind of follow my gut and make a lot of educated guesses.”
McCullough, who filmed scenes for the movie intermittently throughout 2023 and 2024, said he felt like part of a family when he was on set. Director Julius Onah was kind and welcoming, and Anthony Mackie, who plays Captain America, instantly felt like an old friend. Mackie gave McCullough one of his favorite cigars on the first day they filmed together, and Marvel Co-President Louis D’Esposito chatted with McCullough at the film premiere in Los Angeles.
“I’m just a working class actor, and it just really touched me that the producers and the top level folks at Marvel took the time to really make me feel like I was part of the Marvel family. That meant a lot to me,” McCullough said.
He said some of his most meaningful acting projects have been the ones that remind him of his childhood, including Captain America and a Marvel TV series called The Gifted in which he played a Navy SEAL with mutant superpowers in two 2018 episodes.
“Obviously, the little boy in me loves Marvel Comics,” he said. “I loved the Captain America character. I’m a huge fan of the MCU (Marvel Comics Universe).”
Growing up, he was also a fan of the TV show Quantum Leap, so he was thrilled to appear in an episode of NBC’s reboot in 2022 and talk with one of the original show’s producers and writers. He also loved the Karate Kid movies and had the opportunity to appear in an episode of Netflix’s Cobra Kai series and work with lead actor Ralph Macchio.
“I remember having the biggest, silliest grin on my face and just thinking, ‘If you told the 8-year-old me that one day I’d be getting in a fight with the Karate Kid, I never would have believed you in a million years,’” McCullough said. “The connections to my childhood and playing make-believe as a kid, that’s kind of the biggest joy for me as an actor.”
One of his most enjoyable recent projects was the 2024 film On the Run, for which he rode a motorcycle around New Mexico while playing a former motorcycle gang leader on a quest for vengeance. Coming up, McCullough can be seen in the Amazon series Ballard, a spinoff to Bosch starring Maggie Q; and Final Hour, filmed in an Atlanta prison last year. In the latter, he plays a man on death row who discovers an unlikely connection to a priest who visits him.
When getting into character, McCullough takes an approach that may seem counterintuitive: being himself. He said that method has allowed him to create well-rounded and grounded characters and find success as an actor.
“I just do the scene as if it’s happening to me, and that’s how I interact with the other characters. As long as I’m being truthful and allowing real emotions and real connections in whatever scene I’m doing, some aspect of my personality is going to come through. When you try to pretend that you’re someone else, it’s not nearly as powerful as when you just bring you with all of your many bright spots and many faults,” he said.
“That’s been the way that’s allowed me to go from struggling as an actor doing student films, short films and low budget films that I hope you never find online to working on stuff I’m really proud of. When I stopped ‘acting’ and started being, it changed everything.”
Currently, McCullough’s main focus is developing a TV comedy with his production company, Fort Argyle Films. The series is inspired by the life of his dad and his best friends growing up in Savannah and will be filmed there.
McCullough said his dad had the most profound influence on his career, showing him that he didn’t need to transform himself for others but only be his most authentic self. Los Angeles actor Jack Plotnick also helped McCullough to overcome self-doubt and learn how to “turn my dreams into a career that paid my bills.”
McCullough said he “made every mistake an actor can make” in the early years, and he feels an obligation to help others, so they don’t have to learn the hard way. He teaches and mentors aspiring actors through his business Working Actor Lab.
“I think it’s very easy — for anyone but certainly for actors — to get complacent at whatever level you’re at, and for me, that just gets old fast,” he said. “I always want to play more impactful roles in bigger and bigger projects, and I’ve been very fortunate to be able to do that.”
