The following description is from the National Park Service's website:
"In July 1865, three months after the restoration of peace between the states, Congress authorized the establishment of a National Cemetery in Fredericksburg to honor the Federal soldiers who died on the battlefields or from disease in camp. The site chosen was on Marye's Heights, the formidable Confederate position which had proven so impregnable to repeated Federal attacks on December 13, 1862. The cemetery contains the graves of over 15,000 United States soldiers. Most of them are Union soldiers who died in the battles and camps around Fredericksburg. About 100 soldiers are 20th century veterans including at least two spouses. Over 80% of the soldiers are unknown."