Statistics for occurrence #1 of “York rivers” in chapter 13 of The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 5: Forts and Artillery.:

...-yard, at which the Merrimac, some time later, was converted into the ironclad Virginia, and the guns needed for the speedy armament of batteries for the defense not only of the Elizabeth, James, and York rivers , but also against attacks on Norfolk and Richmond by other lines of approach, were obtained. Subsequently, the Virginia Corps of Engineers was merged into that of the Confederate States; and the ...
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