Mess Wagon

The “mess wagon” is an earlier name for the “chuck wagon” (designated the official Texas state vehicle by the legislature). The term “mess wagon” was current in the early 1860s, so Charles Goodnight could not have invented the “chuck wagon” in 1866.
 
The cook often served as driver of the mess wagon. In the back of the mess wagon was a pantry called a “mess box” (or “chuck box”).
 
 
Wikipedia: Chuckwagon
A chuckwagon was originally a wagon that carried food and cooking equipment on the prairies of the United States and Canada. They would form a part of a wagon train of settlers or feed nomadic workers like cowboys or loggers. It was common for the “cookie” who ran the wagon to be second only to the “trailboss” 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 chuckwagon is accredited to Charles Goodnight, a Texas rancher who introduced the concept in 1866. Chuck was then a slang term for food. Chuckwagon 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 chile peppers were planted along the cattle trails to serve for future use.
 
Google Books
The Life of Nathanael Greene, Major-General in the Army of the Revolution
edited by William Gilmore Simms
New York, NY: Derby & Jackson
1861
Pg. 376:
General Caswell’s mess-wagon afforded the best refreshment; very unexpectedly to the writer, he there found a pipe of good Madeira, broached and surrounded by a number of soldiers, whose appearance led him to inquire what engaged their attention.
     
1 December 1865, Cedar Falls (Iowa) Gazette, pg. 2, col. 2:
Three miles above Spring Hill the firing grew more lively, and as we were about a mile in advance of our wagon, (George, with the mess wagon, was back with an ox train of seventeen wagons,) and as we were somewhat tired, having left our riding horses with the train in the rear, we thought it best, safest and wise in us to halt awhile. 
 
Live Search Books
Muskingum Legends
by Stephen Powers
Philadelphia, PA: J. B. Lippincott & Co.
1871
Pg. 244:
The train was to leave Waxahatchie the next day, and I accordingly carried out my roll of blankets, etc., and deposited them in the mess-wagon. 
   
4 July 1885, Decatur (IL) Daily Republican, “Range Riding: Stirring Scenes of the Season in the Montana Cow Camps,” pg. 2, col. 3:
And now a few words regarding the “mess” of the cow-camp. The cooks and cookees take charge and drive the mess-wagons, with their camp equipment, from place to place during the round-up periods. Almost invariably the cooks are professionals, and the cooking is excellent. With delicious, juicy Montana beef, with bread made from Dakota wheat, and with many of the vegetables and fruits supplied by the “canners,”—all prepared, usually, in a manner to suit the most particular tastes,—the meals, whether spread upon the green grass or upon the tables made by letting down the doors of the mess wagon mess-boxes are, as a rule, greatly relished by all who try them., and are far more satisfying than the dinners of many a first-class hotel.—Miles City Cor. Chicago Tribune.
 
Google Books
Ranch Life and the Hunting-Trail
by Theodore Roosevelt
New York, NY: The Century Co.
1888
Pg. 48:
Occasionally there will be two wagons, one to carry the bedding and one the food, known, respectively, as the bed and the mess wagon; but this is not unusual.
 
14 October 1890, Bismarck (ND) Daily Tribune, pg. 4:
Where there was a light there must be life, and with renewed hope I galloped off in that direction, and about ten minutes later had the satisfaction of seeing the canvas top of the mess wagon coming up before me.
 
14 August 1892, Columbus (OH) Enquirer-Sun, pg. 3:
I took my camera along and got some pictures of our supper group, the mess wagon, cowboy-cook, cowboys, ponies and ladies, all in a bunch, and it was to these my companion (the cook) referred.
       
25 November 1892, Galveston (TX) Daily News, “Out on a Cattle Trail,” pg. 3, col. 3:
With them went a mess wagon, or, speaking in cowboy vernacular, “chuck wagon,” a cook—who was also driver—a horse rustler, from eight to ten riders and a boss, who was also a rider when occasion demanded.
 
Google Books
Cowboy Lingo
by Ramon F. Adams
Boston, MA: Houghton Mifflin Company
1936
Pg. 146:
Cooks drove their own wagons in moving camp and as a class they were reckless drivers. Most of them “jes’ throwed the lines away an’ herded his four hosses across the country.” Usually in the lead galloped a “pilot,” a man familiar with the country and chosen to pick a route over sagebrush, greasewood, and dry washes for the careening “mess-wagon” hauled at breakneck speed. If a second wagon was hooked onto the chuck-wagon, as was sometimes the case in moving camp, it was called the “trail wagon.” 
 
Google Books
The Cowboy at Work
by Fay E. Ward
New York, NY: Hastings House
1958
Pg. 37:
The chuck wagon, or mess wagon, is an ordinary lumber wagon in which is installed a mess-box, or chuck-box, set in the rear end of the wagon-box as shown in the illustrations on Plate 9.
     
Google Books
Dictionary of the American West:
Over 5,000 terms and expressions from Aarigaa! to Zopilote
by Winifred Blevins
Seattle, WA: Sasquatch Books
2001
Pg. 236:
MESS BEEF A pickled or salted beef of early Texas. The mess house was the ranch cookhouse, the mess room the cowboys’ dining room, and the mess wagon the CHUCK WAGON (which had a storage box called the mess box) or the freighting wagon carrying the provisions.