Ken Martin,
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Below is my bibliography entry for the map that you referenced in your posting. This huge book adorns my shelf.
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"Atlas to Accompany the Official Records of the Union and Confederate Armies," Wash D.C., Govt. Printing Office (1891), reprinted 1978 by Arno Press NY, with title "The Official Military Atlas of the Civil War." Key to this study is a Dec 31, 1860 map that shows the “False Washita — referenced four times in the Official Record — or Rio Negro” which was later called the Washita River (Faux Quachita in some records).
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re: Preston, OK? An attendee of a Plano TX speech approached me to state that he had inherited the original Preston property north of Red River. ..And yes, I did an about face questioning "Preston TX" vs. "Preston OK," but the family has had this property for generations, with cabins, etc.
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re: Ft. McCulloch. ..I agree that Ft. McCulloch is misplaced on this 1860 map. ..... That's why we need several maps depicting the same area in an era of our studies. ... Sort of analogous to a woman shaving her legs: "Hit and miss, what I don't get today, I'll get tomorrow." ... ..i.e., No map has all info. ..Besides, we love to study maps, the more the merrier, and I love to index, in my gazetteer, every place mentioned.
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Patti, prochette@Juno.com