A chuck wagon was originally a wagon that carried food and cooking equipment on the prairies of the United States and Canada. They were part of a wagon train of settlers or nomadic workers like cowboys or loggers. It was common for the 'cookie' who ran the wagon to be second only to the 'trail boss' on a cattle drive. The cookie would often act as cook, barber, dentist, and banker.

While some form of mobile kitchens had existed for generations, the invention of the chuck wagon is attributed to Charles Goodnight, a Texas rancher who introduced the concept in 1866. Chuck was then a slang term for food. Chuck wagon food included easy-to-preserve items like beans and salted meats, coffee, and sourdough biscuits. Food would also be gathered en route. In Texas, it is said that chili peppers were planted along the cattle trails to serve for future use. 

Chuckwagon etiquette
On the old time cattle drives and roundups, the cook was sometimes an aging cowboy hired for his ability to drive a wagon more than his cooking skills. He was in charge of the wagon and everything related to it.  The cook was paid more than the other hands because the success of the camp and the drive depended greatly on him and the cook's job was arguably the hardest.  A cowhand earned about a dollar a day and the cook made twice that.   Ranch cooks today still command a great deal of respect and most expect a certain strict etiquette in their vicinity. 
Cowboys were forbidden to eat at the chuck wagon table-that was where the cook prepared the food.  A cowboy never rode their horse through the 'kitchen.'  The cowboys always rode downwind of the wagon, so the dust they stirred up wouldn't blow into the food.
At mealtime, cowboys got their own plate, fork, knife, and cup.  The cook would pour the coffee and the cowboys helped themselves to staples like hot biscuits, beef steak, and beans.  When they were done, they stacked their dishes for the cook to wash.