what does Four score and 7 years mean ?
A score is 20 years, so 4 score and 7 years ago would be 87 years.
It's from Lincoln's Gettysburg Address - the country was 87 years old when he spoke - from 1776 to 1863
November 19, 1863:
"Beginning with the now-iconic phrase "Four score and seven years ago," Lincoln referred to the events of the American Revolution and described the ceremony at Gettysburg as an opportunity not only to dedicate the grounds of a cemetery, but also to consecrate the living in the struggle to ensure that "government of the people, by the people, for the people, shall not perish from the earth.