Can you point me to a source that names those 300 newspapers?
I couldn’t find a list, just mention of some of the larger and more well known papers.
“You will take possession by military force, of the printing establishments of the New York World and Journal of Commerce . . . and prohibit any further publication thereof . . . You are therefore commanded forthwith to arrest and imprison . . . The editors, proprietors and publishers of the aforementioned newspapers. (Order of Abraham Lincoln to General John Dix, May 18, 1864)”