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Improvement Era ended in 1970.
When it was formed, it was in the Mesozoic era, but it ended in the Cenozoic era.
T68
Paleozoic era
It ended about 65 million years ago
The Cenozoic era started 65 million years ago.
At the Threshold of an Era ended on 1999-12-18.
Era of good feelings
Diaz
Mesozoic
I believe it was 1877
The Mesozoic era began roughly 250 million years ago, and ended 65 million years ago. (This Era ended because of the K.T. extinction)