This Memorial Day – marking 55 years since the holiday was fixed to the last Monday in May – honors those who gave their lives in service to a grateful nation, tracing its roots to Decoration Day and to the May 1, 1865 ceremony by formerly enslaved people in Charleston, S.C., who planted flowers on the graves of 257 Union soldiers months before other national commemorations.

Many people visit cemeteries and memorials on Memorial Day, this year observed on May 25.