Short answers, pulled from the story.
The bloodiest single day in American history occurred on the 17th of September 1862. General Robert E. Lee's first invasion of the North ended there when Union forces halted his advance.
Congress established Antietam National Battlefield Site on the 30th of August 1890 to preserve the ground where over 22,000 men died or were wounded. This designation transferred control from the War Department to the federal government before the land passed to the National Park Service in 1933.
Antietam National Cemetery holds more than 4,976 interments within its borders after opening its gates to the dead in 1867. Only about 40% of the remains could be successfully identified during the initial burial efforts.
The American Battlefield Trust purchased the 44.4-acre parcel for about $1 million in 2015 and returned the land to its wartime appearance by mid-2023. The organization removed postwar houses and barns that had stood on Hagerstown Pike since the war ended.
The first Saturday in December marks an annual tradition that began in 1989 on the northern portion of the battlefield. Over a thousand volunteers gather each year to place 23,000 luminaries in neat rows across the grass to honor soldiers killed or missing.