Briefly: Modernity, 1889-1914

Modernism, the great Jacques Barzun observes, "rightly belongs to those twenty-five years [1889-1914] in which nearly every idea in the twentieth century was hatched." A Stroll with William James.

The catalogue of neat stuff that drives us today either started or became widespread during those 25 years: skyscrapers, welfare programs, divorce, universal literacy, abstractionist art, public libraries, movies, Coca-Cola, fingerprinting, etc. and etc.

Further reading: Jacques Barzun, From Dawn to Decadence, 591 et seq.