Most societies have stories or narratives of a "golden age" (or ages) when the nation, people, or world were at peace and behaved honorably. Often these golden ages appear at the origins or founding of a society.
In Western Civilization and American culture, selective "golden ages" might include . . .
The Garden of Eden (Genesis)
"The Glory that was Greece, the Grandeur that was Rome"--see classical myths of the Golden Age
The Apostolic Generation when those who knew Jesus awaited his return as a community--see Book of Acts
the Renaissance (for art conoisseurs)
The Pilgrims (1600s)
The Founders (late 1700s)
The Greatest Generation (World War 2)
Recent decades of perceived prosperity or liberation? (e.g. 60s as Civil Rights, 70s as sexual liberation / equality, 80s as Reagan family values and Cold War victory, 90s as peace and prosperity, 2000s as hope-your-daddy's rich?
For American Indians: America before contact with Europeans
For African Americans: Civil Rights Movement of mid-20c; Some nostalgia for Africa before incursions of New World slavery