Came across this handy site during my internet travels this morning…Shotgunrules.com
The history of calling “Shotgun” goes back to the days of covered wagons and the Wild West. On a trip across the plains, the driver of a wagon would hold the reins of his horse team and concentrate on driving. This left him and the occupants of his wagon susceptible to sneak attacks from bandits and thieves. To avoid this atrocious circumstance it became necessary for one person to sit next to the driver with a shotgun and fend off the enemy.
History, rules plus a handy pocket reference guide. It’s something every Motorer should have!