Born and raised in Oklahoma, Sparks began following a path to becoming a chemical engineer at Oklahoma State University but eventually shifted to acting. Relocating to New York City, he paid his dues, like many local actors, in guest spots on the procedural drama "Law & Order" (NBC, 1990-2010) and its spin-offs, before venturing into the theater world as an understudy in the sports-themed Broadway show "Take Me Out." In 2006, he had a stint on the cable family saga "Brotherhood," starring Jason Clarke and Jason Isaacs, and portrayed a detective in both the thriller "Deception" (2008), featuring Hugh Jackman, and the tense drama "Afterschool" (2008). Sparks' reputation as a supporting player in films was furthered that year with parts in the Charlie Kaufman indie oddity "Synecdoche, New York" and the lauded Jonathan Demme sister-centric tale "Rachel Getting Married," starring Anne Hathaway and Rosemarie DeWitt. Sparks' breakthrough role came in 2010, when he signed on as bootlegging tough guy Mickey Doyle on the Prohibition-era ensemble drama "Boardwalk Empire," appearing as a regular along with Steve Buscemi, Michael Shannon, Kelly Macdonald and Shea Whigham. Drawing inspiration from real-life Atlantic City bootlegger Mickey Duffy, Sparks proved to be a reliably intimidating presence on the series, and this increased visibility led to further opportunities. In 2011, he was featured in one installment of HBO's star-studded period miniseries "Mildred Pierce," based on the melodramatic James M. Cain novel, and later that year, he had a notable part in the war-vet drama "Return," starring Linda Cardellini and his "Boardwalk Empire" peer Shannon. He worked on the same production as Shannon yet again for the acclaimed Southern-set thriller "Mud" (2012), which showcased Sparks as Carver, a fierce criminal in pursuit of Matthew McConaughey's on-the-lam title character. Sparks had a particularly busy year in 2013-in addition to his ongoing "Boardwalk Empire" role, he appeared on the comedy series "Underemployed" (MTV, 2012-13) and in Clark Gregg's Hollywood satire "Trust Me," as well as another historical production, the 1960s-set feature drama "Parkland," which focused on the day of John F. Kennedy's assassination.