A sort of flags have been designed for naval battles at some point of the Civil War; these blanketed distinguishing marks for ships

https://dominickuqhq312.greyhavendaily.com/posts/from-cotton-to-canvas-the-materials-behind-civil-war-flags-3

A form of flags have been designed for naval battles all the way through the Civil War; these incorporated distinguishing marks for ships engaged in strive against on rivers and seas alike.