In the Old West of the US, stagecoaches carried passengers, freight, mail and money- and could be robbed. The driver sometimes had a guard that rode beside him on the seat, who was armed- usually with a shotgun.
Riding Shotgun - 2012 V is rated/received certificates of: Australia:MA
Old stagecoaches had two people sitting on top of the carriage. One was the driver, the other carried a shotgun to defend against Indians and bandits. Riding beside the driver is riding shotgun.
"Riding shotgun" means sitting in the front seat of a car. Before a car journey, if you are quick, you can call shotgun and you get to sit in the front seat.
The term can from the old days when there was a stagecoach driver and an armed guard with a shotgun to protect the coach from being robbed. Side Note: It didn't always work.
Riding Shotgun - 2013 was released on: USA: 4 October 2013 (Woodstock Film Festival)
Greensburg Kentucky
The cast of Riding Shotgun with Jack McConaha - 2005 includes: Jack McConaha as himself
Riding shotgun?
Lawman - 1958 Riding Shotgun 1-29 was released on: USA: 19 April 1959
The present-participial phrase "riding a horse" is an adjective, modifying sheriff.
Manga Motion Comics - 2009 Riding Shotgun 1-3 was released on: USA: 1 January 2009
Riding Shotgun - 2004 was released on: USA: 14 May 2004 (Los Angeles, California) USA: 18 September 2004 (Cinema Paradise Film Festival)