Statistics for occurrence #1 of “Northern Virginia” in chapter 1 of The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 4: The Cavalry:

... of mounted troops. They began with the great combat of Beverly Ford, Virginia, June 9th, in which for twelve hours, eighteen thousand of the flower of the horsemen of the armies of the Potomac and Northern Virginia , in nearly equal proportions, struggled for supremacy, with many casualties, parting by mutual consent at the close of the day. This was followed by a series of daily skirmishes during the remainder...
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