The chuck wagon was invented in 1866, when Texas rancher Charles Goodnight converted an old army-surplus Studebaker wagon into a mobile kitchen to feed cowboys while driving cattle from Texas to New Mexico.
The wagon itself carried everything you could possibly need. A Dutch oven was important for cooking, along with food such as beans, salted meat, sourdough biscuits, dry fruit, a water barrel, guns, ammo, farrier supplies, ropes, lanterns, firewood, kerosene, slickers, bandages, coffee, tobacco and alcohol. If a cowboy or calf was injured, they would ride in the back of the chuck wagon.
The second highest ranking cowboy out on the cattle drive, sitting just below the trail boss, was the cook, or "cookie" as they were referred to. The cookie and his chuck wagon had to be far enough in front of the cowboys as to have a meal prepared by the time they arrived in camp. The cookie tended to the injured, and his chuck wagon was "home" out on the range, as the cowboys always gathered around to eat and sleep.