The First Zoological Society in the US was formed in Philadelphia.
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A newly discovered water beetle was named after Leonardo DiCaprio.
President Richard Nixon signed the US Endangered Species Act into law.
The first motion picture was shown to a theater audience at the Philadelphia Academy of Music.
The Pyrenean ibex went extinct after the last surviving member of the species was killed by a falling branch.
Delegates started to gather in Philadelphia to draw up the US constitution.
