The story
Literally, “87 years ago” (score sense: “group of 20”) the beginning of the Gettysburg Address made on November 19, 1863, by United States President Abraham Lincoln (1809–1865). The widespread familiarity of Lincoln’s address, the unusual and poetic wording, and its status as the first words of the speech have caused the phrase to enter the public consciousness.
Etymology from Wiktionary, CC BY-SA 4.0.