Riding Shotgun
Every time a group of people takes a car ride, they are all aware that the front passenger seat is the best one. The vista, the music, and not having to drive while paying attention gives you the best of both worlds. As a result, it is an unwritten rule of the road that those who wish to sit in the front passenger seat may "call shotgun," and those who are successful in doing so are said to "ride shotgun."
When stagecoaches had to forge the frontiers and frequently met with outlaws, Native Americans, and even wild animals, riding shotgun evokes the Wild West. As a result, the job title "shotgun messenger" was created, designating a guard to ride alongside the driver while carrying, you guessed it, a shotgun.
Although the custom was undoubtedly in use in the Wild West, it is still unclear whether the term "riding shotgun" was truly used at the time. The Sunset Trail, a 1905 novel, contains the idiom's earliest known printed instance. However, the phrase became widely used in early Hollywood westerns and was inextricably associated to the Old West.