Statistics for occurrence #1 of “upper Arkansas” in chapter 37 of Philip Henry Sheridan, Personal Memoirs of P. H. Sheridan, General, United States Army .:

...imultaneously with the fiendish atrocities committed on the Saline and Solomon rivers and the attack on Comstock and Grover, the pillaging and murdering began on the Smoky Hill stage-route, along the upper Arkansas River and on the headwaters of the Cimarron. That along the Smoky Hill and north of it was the exclusive work of the Cheyennes, a part of the Arapahoes, and the few Sioux allies heretofore mentione...
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