Sentence:  But tonight the Union veteran of Maryland clasps hands with the rebel veteran of Missouri, and the gap is closed. In this supreme moment the imperfect welding of the broken Union is perfected at last, and from this hour the seam of the joining shall no more be visible. The long tragedy is ended — <WSD>ring down the curtain</WSD>! 
Meaning of the word marked with <WSD> tags:  To mark the end of something.