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What You Didn't Know Mark Harmon Did Before NCIS

Actor Mark Harmon has had a long, storied career that's led him to a large number of different series and film roles. Many procedural fans likely think of him as Leroy Jethro Gibbs, unflappable head of the titular agency in "NCIS" in 18 seasons and counting on the program. While Gibbs has entered the realm of popular culture thanks to this long, storied run, there's much more to Harmon than this one role.

Harmon had some interesting pre-show history behind him that includes several fascinating and unusual accolades and appearances. From parts on cult sitcoms to leading turns in 1980s favorites, this well-traveled veteran actor has been to a lot of places and done a lot of unexpected things. We're pretty confident you don't know about the fascinating turns his career has taken over the past 40-plus years — so keep reading to find out if your knowledge matches ours!

He had fame in his blood before he began to act

Mark Harmon sprung from famous roots. His father, Tom Harmon, was a well-known sports figure — a Heisman Trophy-winning football player for the University of Michigan and the Los Angeles Rams who later became a spokesman and sports broadcaster, per the Los Angeles Times. Tom was also a World War II hero and an actor. Mark's mother, meanwhile, was Elyse Knox, an actress famous for her appearances in the "Joe Palooka" series of B-movies and for her role in the 1942 film "The Mummy's Tomb."

The family's fame doesn't stop there. According to People, Mark's sister Kristin became an actress, then an artist after marrying and divorcing rock legend, TV star, and teen idol Rick Nelson. Kristin was the mother of actress Tracy and twin musicians Matthew and Gunnar of the band Nelson. His sister Kelly, meanwhile, gained fame as a model and from her part in a series of ads for Tic Tacs (via IMDb). Kelly was married to automotive executive John DeLorean from 1969 to 1972.

His St. Elsewhere character was a first for prime-time TV

Before graduating cum laude from UCLA, Harmon was a quarterback for the school's football team from 1972 to 1973. He also got reviews about wooden performances that have nothing to do with his acting; he was once a carpenter by trade, according to IMDb. "NCIS" gives a nod to Harmon's former profession via Gibbs' interest in boat building. 

Aside from his carpentry career, Harmon considered jobs in law and advertising and began work as a merchandising director, according to People. Ultimately, though, he was Hollywood-bound. During the early-to-late 1970s, he racked up a number of bit parts and guest-starring roles on well-known sitcoms — the first was on the short-lived Harriet and Ozzie Nelson show "Ozzie's Girls" in 1973. He appeared on the first season of "Laverne and Shirley" and on shows such as "Emergency!" on his way to receiving an Emmy nod for playing Robert Dunlap in the miniseries "Eleanor and Franklin: The White House Years" in 1976. A minor role in the disaster epic "Beyond the Poseidon Adventure" followed.

Harmon's career reached new heights in the mid-'80s, starting with a part on the medical dramedy "St. Elsewhere.For three seasons, he portrayed hunky Dr. Robert Caldwell and was written off the program when his character died offscreen after contracting HIV due to an unprotected sexual encounter — a first for primetime television, per Rotten Tomatoes.

From cult hits to leading man

Fans of a certain generation probably best remember Harmon as Freddy Shoop from the 1987 cult hit film and eventual cable TV staple "Summer School", or perhaps as People's Sexiest Man Alive for 1986. Around the same time, he was also a spokesman for Coors Beer, which ran a number of ads featuring the actor from 1985 to 1987. In 1988, he starred in "The Presidio" with Meg Ryan and Sean Connery, then led the 1988 Jodie Foster film "Stealing Home." After the box-office failure of the 1989 film "Worth Winning," he worked more frequently on stage and on TV.

He went on to portray Dr. Jack McNeil on the long-running CBS medical drama "Chicago Hope" from 1996 to 2000, directing two episodes of the show along the way, before joining "NCIS" in 2002.

Offscreen, Harmon became a part owner of the minor baseball team San Bernardino Spirit in 1988, per the Los Angeles Times, and used the team's home ballpark in the "Stealing Home." He and actress Pam Dawber ("Mork and Mindy," "My Sister Sam") have been married since March 21, 1987, and they have two sons, Sean Thomas (who has portrayed a younger version of Gibbs on episodes of "NCIS") and Ty Christian.