Wife of Jonathan Cost.
Age 76 years.
Source: Cemetery Inscriptions from Loudoun County, Virginia: Copied & Typed by Mrs. Walter Towner Jewell, Arlington, Virginia: Digitized by the Internet Archive in 2009 with funding from Family Search
Additional information provided by Andy (#47594735):
Martha Cost is the mother of Sgt William Flavius Cost.
I have researched his history in depth. I have written a story about him and his friend, Benjamin G. Hill. They both served together in the "11th New York Cavalry". William stayed in Washington, DC and guarded Pres. Lincoln during the civil war.
MARTHA A. / Wife of / JONATHAN COST. / Died / Aug. 2, 1877, / Aged / 76 Yrs. 6 Mos. 25 Ds.