In the Spring of 1866, Henry C. Welles, a druggist in the village of Waterloo, NY, suggested that the patriots who had died in the Civil War should be honored by decorating their graves. General John B. Murray, Seneca County Clerk, embraced the idea and a committee was formed to plan a day devoted to honoring the dead. Townspeople made wreaths, crosses and bouquets for each veteran's grave. The village was decorated with flags at half mast. On May 5 of that year, a processional was held to the town's cemeteries, led by veterans. The town observed this day of remembrance on May 5 of the following year as well.

Decoration Day was officially proclaimed on May 5, 1868 by General John Logan in his General Order No. 11, and was first observed officially on May 30, 1868. The South did not observe Decoration Day, preferring to honor their dead on separate days until after World War I. In 1882, the name was changed to Memorial Day, and soldiers who had died in other wars were also honored.

In 1971, Memorial Day was declared a national holiday to be held on the last Monday in May.

Today, Memorial Day marks the unofficial beginning of the summer season in the United States. Memorial Day Weekend is a three-day holiday that is typified by the first family picnics and barbecues of the year. The Indianapolis 500 Mile Race takes place on the Sunday before Memorial Day.