From your identification, I went on to find this. Thanks Sue Moore
"General McCulloch, at the head of a column including the Texas cavalry units, occupied Springfield for a brief period after Fremont's evacuation of the city, during which he pondered an attempt on St. Louis. He elected to retire with his command toward the Arkansas line, however, and during the first week in December,[1861] the various regiments went into winter quarters. The Sixth chose the name Camp Washington for their location a few miles downstream from the mouth of Frog Bayou on the Arkansas River, where the Third was camped."
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" From the rustic pleasures of winter quarters, the Sixth and Third regiments, along with the recently-joined Eleventh Texas Cavalry and Whitfield's Battalion, were turned out late in December to chastise the irrepressible Hopotheohola, who had undertaken a winter campaign against Cooper and his Indian brigade. The command crossed the Arkansas River at Van Buren, where it was joined by a regiment of mounted infantry, and began a forced march to Fort Gibson in bitter cold. Seventy miles beyond Fort Gibson, Hopotheohola, a former principal chief of the Creek Nation, had posted his Indian troops atop a precipitous eminence overlooking Chustenahlah Creek in the Cherokee Nation, where the Confederate forces located them on the afternoon of Christmas Day."
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Dec 14th 1861 Camp Washington
[to] Wm Gibbard Esq

My Dear friend, Your favor of the 16th Nov is at hand. I was pleased to learn from it that you & family, & the citizens of the Grove were in good health. ...Nothing of interest have transpired since I wrote you last, only our fall campaign was closed without having a fight, we are now camp[ed] near our quarters, we are building cabins & Stables, we have quite a healthy location, we are some two miles from the Arkansas River, 12 miles below Ft Smith. The health of our Regiment is bad, a great many of the boys are sick, their sickness is the measles mumps & Fever, some 12 or more men have passed from off the stage of action ....[ signed] David R. Garrette [Co. E, 6th TX Cav.]

from The Civil War letters of David R. Garrette, detailing the adventures of the 6th Texas Cavalry, 1861-1865, Author: Garrett, David R; Lale, Max Sims; Key, Hobart, Jr., Marshall, Texas, Port Caddo Press, [Public domain] 1923 – 1963.