Arlington National Cemetery is a cemetery in Arlington County, Virginia. People who served in the United States military are buried here. The cemetery started during the American Civil War. It is on a big farm called Arlington House. Arlington House was the home of Mary Anna Custis Lee. Mary Anna Custis Lee was a great-granddaughter of Martha Washington. She was also the wife of Confederate general Robert E. Lee. Although most of the farm now has graves, the old farmhouse still stands in the middle of the cemetery. The cemetery is across the Potomac River from the Lincoln Memorial in Washington, D.C..