Statistics for occurrence #1 of “upper Mississippi” in chapter 28 of Admiral David D. Porter, The Naval History of the Civil War.:

...men who never shrunk from any dangerous service,--only one steamer was sunk by the enemy's shot. A sufficient number of gun boats had been left at the mouth of the Yazoo River to take care of the upper Mississippi , and to look out for two formidable rams that were building at Yazoo City, forty miles from the mouth of the river. Sherman remained with his division at Young's Point, ready to make another atta...
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