Title: Mark Harmon
Content:  an honorable Union cavalry officer. During the mid to late 1970s, Harmon made guest appearances on TV series such as Laverne & Shirley, Delvecchio, The Hardy Boys/Nancy Drew Mysteries and had supporting roles in the feature films Comes a Horseman (1978) and Beyond the Poseidon Adventure (1979). He then landed a co-starring role on the 1979 action series 240-Robert as Deputy Dwayne Thibideaux. The series centered around the missions of the Los Angeles County Sheriff's Department Emergency Services Detail, but was also short-lived. In 1980, Harmon gained a regular role in the prime time soap opera Flamingo Road, in which he played Fielding 
Title: Mark Harmon
Content:  the husband of Morgan Fairchild's character. Despite initially good ratings, the series was canceled after two seasons. Following its cancellation, he landed the role of Dr. Robert Caldwell on the series St. Elsewhere in 1983. Harmon appeared in the show for almost three seasons before leaving in early 1986 when his character contracted HIV through unprotected intercourse, one of the first instances where a major recurring television character contracted the virus (the character's subsequent off-screen death from AIDS would be mentioned two years later). In the mid-1980s, Harmon also became the spokesperson for Coors Regular beer, appearing in television commercials for them. Harmon's 
Title: Mark Harmon
Content:  After college, Harmon considered pursuing a career in advertising or law. Harmon started his career in business as a merchandising director, but soon decided to switch to acting. He spent much of his career portraying law enforcement and medical personnel. One of his first national TV appearances (other than as an athlete) was in a commercial for Kellogg's Product 19 cereal with his father, Tom Harmon, its longstanding TV spokesman. Thanks to his sister Kristin's in-laws, Ozzie Nelson and Harriet Nelson, he landed his first job as an actor in an episode of Ozzie's Girls. This was followed by guest roles in episodes of 
Title: Mark Harmon
Content:  Police Woman, and Emergency! in mid-1975. He also performed in "905-Wild", a backdoor pilot episode for a series about two L.A. County Animal Control Officers which did not sell. Producer/creator Jack Webb, who was the packager of both series, later cast Harmon in Sam, a short-lived 1978 series about an LAPD officer and his K-9 partner. Before this, Harmon received an Emmy nomination for Outstanding Supporting Actor in a Miniseries or a Movie for his performance as Robert Dunlap in the TV movie Eleanor and Franklin: The White House Years. In 1978, he appeared in three episodes of the mini-series, Centennial, as Captain John 
Title: Mark Harmon
Content:  a limited engagement on the series Moonlighting, playing Cybill Shepherd's love interest Sam Crawford for four episodes. He then starred in the 1987 TV movie After the Promise. In 1988, he co-starred with Sean Connery and Meg Ryan in the 1988 feature film The Presidio, and also opposite Jodie Foster in the film Stealing Home. Despite several high-profile roles, Harmon's film career never gathered momentum and, after a muted reception to his 1989 comedy Worth Winning, he returned to television, appearing in various television movies. Harmon's next regular television role would be as Chicago police detective Dickie Cobb for two seasons (1991–1993) on 
Title: Mark Harmon
Content:  Harmon is the son of football player Tom Harmon and actress Elyse Knox. His sisters are Kelly, an actress and model, and Kristin, an actress and painter. Kristin died of a heart attack on April 27, 2018. Harmon worked as a carpenter before making a success of his acting career. On NCIS, his carpentry skills are alluded to through his character's hobby of building boats in his basement. Harmon has been married to actress Pam Dawber since March 21, 1987. The couple have two sons: Sean Thomas Harmon (born April 25, 1988), who has played a young Gibbs in several NCIS episodes, and Ty Christian Harmon (born June 25, 1992). They 
Title: Mark Harmon
Content:  In 2003, Harmon had a supporting role in the remake of the comedy film Freaky Friday. Harmon has also starred in several stage productions in Los Angeles and Toronto. At the Cast Theatre in Los Angeles, he performed in Wrestlers and The Wager. In the late Eighties he was part of the cast of the Canadian premiere of Key Exchange. Several productions of Love Letters provided him the opportunity to play alongside his wife Pam Dawber. Harmon received the 2,482nd star of the Hollywood Walk of Fame on October 1, 2012. In 2014, Harmon started a production company called Wings Productions to produce NCIS: New Orleans. As of 2018, Harmon works as a producer for a new CBS series, based on author John Sandford's best-selling Prey novels, which have sold more than 30 million copies worldwide. The last 10 have reached No. 1 on The New York Times best-seller list. Harmon also directed two episodes of Chicago Hope in 1999 and 2000. He also directed two episodes of Boston Public in 2002.
Title: Mark Harmon
Content:  reached several other high points in 1986. In January, he was named People magazine's Sexiest Man Alive. Following his departure from St. Elsewhere in February, he played the lead in the TV movies Prince of Bel Air, co-starring with Kirstie Alley, and The Deliberate Stranger, in which he portrayed the real-life serial killer Ted Bundy. With his career blossoming, he played a role in the 1986 theatrical film Let's Get Harry and the lead role in the 1987 comedy Summer School, again co-starring with Kirstie Alley and alongside future JAG and NCIS alum Patrick Labyorteaux. Returning briefly to episodic television in 1987, Harmon 
Title: Mark Harmon
Content:  NBC series Reasonable Doubts. In 1993, he appeared in one episode in the role of a rodeo clown on the CBS comedy/western series Harts of the West with future castmate Sean Murray, who plays McGee on NCIS. In 1995, Harmon starred in the ABC series Charlie Grace, in which he portrayed a private investigator. The series lasted only one season, after which he returned to ensemble medical shows on the series Chicago Hope, in which he played Dr. Jack McNeil from 1996 to 2000. He also portrayed astronaut Wally Schirra in one episode of the 1998 mini-series From the Earth to the Moon.
Title: Mark Harmon
Content:  Thomas Mark Harmon (born September 2, 1951) is an American actor, producer, director and former football quarterback. He is best known for playing the lead role of Leroy Jethro Gibbs in NCIS. He also has appeared in a wide variety of roles since the early 1970s. Initially a college football player, his role on St. Elsewhere led to his being named "Sexiest Man Alive" by People in 1986. After spending the majority of the 1990s as a character actor, he played Secret Service special agent Simon Donovan in The West Wing, receiving a 2002 Emmy Award nomination for his acting in a four-episode story arc. Harmon's character of NCIS special agent Leroy Jethro Gibbs was introduced in a guest starring role in two episodes of JAG. From 2003 to 2021, Harmon starred in the spinoff NCIS as the same character.

Question: what tv series did mark harmon star in?
Answer: NCIS.