Addressed to Culpeper C H, Virginia. Manuscript "Belmead Mills, VA May 17, 1861" and pen cancel.

According to the Confederate States of America Catalog and Handbook of Stamps and Postal History:

“On November 15, 1860, Governor John Letcher called for a Special Session of the General Assembly to consider secession. On January 7, 1861, the legislature authorized a Secession Convention to convene on February 13 in Richmond. On April 17, the convention adopted an Ordinance of Secession on condition of ratification by a statewide referendum. The voters overwhelmingly approved the measure on May 23 thus ratifying the terms stipulating the effective date of secession as of April 17, 1861. Virginia was admitted to the Confederacy on May 7.”

Therefore, this cover represents Confederate usage of U.S. Postage.