High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Buchanan County is a county located in the U.S. state of Virginia. As of the 2000 census, the population was 26,978. Its county seat is Grundy. As of 2006, it was the poorest county in the state of Virginia and one of the 100 poorest counties in the United States, when ranked by median household income. The county was formed in 1858 from parts of Russell County and Tazewell County. It was named for James Buchanan, 15th President of the United States (1857-1861).