In searching for Cantonment Washington I noticed some dialog in messages from last year. I believe Camp/Cantonment Washington was the same place as 61-62 winter quarters of part of the 6th Texas Cavalry and may have been at the mouth of Lee's Creek on the Arkansas River. Most of the references I've seen for camp Washington have been from the end of 61, beginning of 62 time frame,some of them referencing Lee's Creek. From the last paragraph before chapter 24 of A W Sparks book (the complete book is on line- search google- Recollections of The Great War A W Sparks freepages) he says
"the winter quarters of 3rd was selected at the mouth of Frog Bayou on the Arkansas River and that of the 6th a few miles down". I've also seen reference to parts of the 6th at Mulberry Creek. The mouth of Lee's Creek is at Van Buren Arkansas at the northern most part of the big bend in the Arkansas River. The mouth of Frog Bayou is east about 10-12 miles as the crow flies and Mulberry Creek is upstream a little, from Frog Bayou. To find these go to terraserver.microsoft and find Fort Smith/Van Buren Arkansas. Zoom in to the fourth level up from (+). Put the northern most part of the big bend in the river at the bottom of your screen. Click on "Topo Map" in the upper right corner. You should now see Lee's Creek. Click south once and east 5 or 6 times and you should see Frog Bayou. You can click back and forth Topo to Aerial to get an idea of where they are. I wish I lived close so I could go have a look. Maybe the Topo Map would help locate troop movements and camps as I think they sometimes reference creeks in diaries and reports.