John Russell was only thirty-seven and looked even younger than that, when he was cast in this series. He believed that in order for a man like Dan Troop to have gained the kind of experience and maturity he possessed, he would have had to have been in at least his mid forties, so Russell had the Make-up Department streak gray through his hair, and he lowered his voice when he spoke, in order to appear several years older.

In season one, Dan was injured a total of six times and shot twice. Johnny was injured four times and never shot. Dan shot and injured seven people, and shot and killed twenty-four. Johnny shot and injured three people and shot and killed twelve. Dan's more interesting injuries include being mauled by a bear and hit by a tree being used as a wagon jack. The most people shot and killed by Dan and Johnny in one episode, in season one were five, in episode twenty-six, "The Gang".

John Russell based his character, Dan Troop, on an officer he knew, when he served in the U.S. Marines.

In the early 1960s, when television western mania reached its peak, an American magazine sponsored a contest for the actors who portrayed western heroes and villains. Since the climactic moment of so many shows was the classic quick-draw shoot-out, the actors had to acquire that skill to play their scenes. The magazine held a competition among some of the stars of the shows, firing blanks, aiming not at each other, but down range, and using an electronic timer. Quite a lot of cowboy stars showed up to slap leather. Peter Brown beat them all, and won the title of the fastest gun in Hollywood.

Adam West made one of three appearances on three separate shows as Doc Holliday. He also portrayed the character on "Sugarfoot (1957)" and "Colt .45 (1957)."

In season two, Dan was injured a total of three times and shot four times (including one graze). Johnny was injured six times and shot three times (including one graze). Dan shot and injured two people, and shot and killed twenty-two. Johnny shot and injured one person and shot and killed ten. Dan's more unusual injuries include stepping in a wolf trap, and being bitten by a child. The most people shot and killed by Dan and Johnny in one episode in season two, were four, in episode eighteen, "To Capture the West".

Speaking of recycled scripts, John Russell got to act out the same story on two different shows. The script featured a retired gunfighter that lets the hero know that he can't use his shooting hand anymore. He goes to the widow of his former business partner and offers her money that rightfully belongs to her. The widow's son refuses, and challenges the gunfighter to a shoot-out. The gunfighter refuses to back down, while the hero tries to talk him out of it. On "Cheyenne (1955)," Russell played the retired gunfighter. On this show, he played the hero trying to talk the gunfighter out of the shoot-out.

Johnny quit his job as Deputy three times during the series run. The first time was when he thought his biological father might have been an outlaw. The second time was when he thought Dan was trying to take credit for a kill that he made. The third time was after he shot a childhood friend, and didn't think he had the stomach for being a lawman anymore.

At the start of season two, Peggie Castle was cast as Lily Merrill, a saloon owner. Over the course of the final three seasons, her relationship with Dan held many similarities with Marshal Matt Dillon and Miss Kitty Russell of "Gunsmoke (1955)" fame.

In season four Dan was injured twice and shot three times (including being grazed once). Johnny was injured seven times, but was not shot. Dan shot and injured eleven people, and shot and killed nineteen. Johnny shot and injured five people and shot and killed nine. Dan's more unusual injury was falling into a hole. The most people shot and killed by Dan and Johnny in one episode in season four, were five, in episode nine, "The Cold One", in which Lily also killed one person. Lily was shot in episode two, "The Juror".

With the death of Peter Brown in March 2016, none of the cast members portraying the three main characters are still alive. John Russell died in January 1991, and Peggie Castle in August 1973.

This was one of the only "Warner Brothers" westerns of the late 1950s to early 1960s that did not have a crossover from one of the other show's stars.

Dan had a brother named Clay. He was portrayed by James Drury.

Eleven comic books based on the series were published from 1958 to 1962.

Recurring character Owny O'Reilly was portrayed as being younger than Johnny McKay. However, in real-life, Joel Grey was three and a half years older than Peter Brown.

In the beginning of the series, Dan and Johnny had a pet cat in the office. The cat disappeared during the course of season one, and its absence was never explained.

In order to attract more female viewers in season two, the producers started having Peter Brown leave his shirt unbuttoned.

Whenever someone fell to the ground, the same sound effect was used, regardless of if they fell off a horse, or while hiding behind a rock.

Johnny's parents were killed when he was only ten-years-old. He was raised by two separate family friends that he referred to as "uncles". Uncle Jess was portrayed by Edgar Buchanan, and Uncle Joe was portrayed by Frank Ferguson.

Beginning in season three, "Warner Brothers" began "toning down" the violence on the show. Instead of killing the villains, Dan and Johnny would still shoot them, but they would only get wounded.

In season three, Dan was injured a total of five times and shot four times (including being grazed twice). Johnny was injured five times, but was not shot. Dan shot and injured two people, and shot and killed twenty-two. Johnny shot and injured three people and shot and killed five. Dan's more unusual injury was being shot in his gun hand, and then having to shoot left-handed. The most people shot and killed by Dan and Johnny in one episode in season three, were four, in episode fourteen, "The Escape of Joe Killmer". Even though other trivia indicates in season three, Warner Brothers began toning down the violence on the show, the numbers did not really reflect this. Dan killed twenty-two people in season two, and twenty-two in season three. Johnny's kills were cut in half, though, from ten to five. Those shot and injured by Dan were two each season, while Johnny's shot and wounded numbers went from one to three.

Dan Sheridan portrayed Jake the bartender at The Birdcage Saloon. Jake's last name was only mentioned one time. It was Summers.

One of the writers listed in the credits is "W. Hermanos", which is a code that meant the script was recycled from another series. W. Hermanos is a Spanish take on the name Warner Brothers.

The series' depiction of the weather in Laramie, Wyoming had the characters regularly sporting large, heavy coats as a result of the cooler climates in the state. This somewhat more accurately reflected the actual average temperatures in Wyoming than other series set in the state, such as The Virginian" or "Laramie." These other series more frequently depicted the weather as warm, as the characters in those series did not wear heavier clothing on a regular basis.