Thanks for the lyrics, Tyghress, but I think you are mistaken about the remains of the Unknown Soldiers being brought to the Lincoln Memorial. Traditionally, the President places a wreath on the Tomb of the Unknowns on Memorial Day. This may also happen at other times, such as when there are visiting heads of state.

I think the song refers to the interment of the Vietnam Unknown on Memorial Day, 1984. Before the interment, the casket lay in state in the rotunda of the US Capitol. "Lincoln's bier" refers to the Lincoln Catafalque, which has been used for many state funerals.

Here is information from the official website of the Tomb of the Unknowns at Arlington National Cemetery.

There is more information at an unofficial site here