Frank S. Edwards joined a volunteer artillery company in St. Louis, Missouri when the Mexican American War broke out in spring 1846. Edwards's company marched over the Santa Fe Trail to help capture and occupy New Mexico. He joined Colonel Alexander Doniphan's Missouri volunteers, who defeated superior Mexican forces at the Battles of Bracito near El Paso and of Sacramento farther south in Chihuahua. His works include A Campaign in New Mexico With Colonel Doniphan (1847).
In the preface, William Cullen Bryant compares the expedition to Xenophon's, which seems like a stretch, but Edwards' observations of a truly remarkable military journey are fresh and outspoken, frequently bigoted. Some things he found exotic now seem everyday, and it's interesting to consider these. While camped at the bull ring in Chihuahua: "I did not see a gentlemanly dog in all Mexico. The pet dogs are called "Comanche:" but why I know not. They are without any hair, and of a dark slate color; and to me, the nastiest animals I know of to look at or to feel. And as to the dogs in general, I should advise a traveller never to stir out without a revolving pistol." (p. 125)
This is simply lightly edited journal entries, but quite interesting for what it is. It includes observations on people, manners, wildlife, geography, architecture, etc. Edwards enlisted as a one-year volunteer in the Missouri militia. He marched (or rode) from Ft. Leavenworth to Santa Fe, Albuquerque, El Paso, Chihuahua, Buena Vista, and Monterey, fighting in two small battles along the way, then took ship for New Orleans and home. He generally thinks little of Mexicans, finding them dirty and impoverished, except for some of the senoritas with lovely large eyes. He especially scorns the cold-blooded murderous brutality of the Texas Rangers.
An interesting document which shows the deeply entrenched racism towards Mexicans and Native Americans, as well as a deep sympathy for them and an interesting first hand account of the southwest during this time.