The modern passport has its beginnings in World War I; it is an outcome of a heightened state of security that kind of stuck around:
The great watershed in the reestablishment of passport regimes among all the major countries of Europe and North America, however, was the First World War, under the declaration of "national emergency." In the political and economic nationalistic environment that followed the war in 1918, passport controls became an institutionalized feature of international travel, with governments reasserting the right to control exit from and entry into national territories under their control. (source)
Before the cash register was invented, retail businesses could only hire from within the family, because they needed to trust the people handling the cash. The invention of the cash register (two innovations, really: the bell ringing when the register is opened, and the tape that recorded every transaction for reconciliation) allowed retail to grow significantly into the massive industry is it today.
Cats. People didn't consider owning pet cats until the nineteenth century, and at first it was a fairly niche thing to do – a lot of young writers, poets, painters would keep cats in their houses, as cats were considered artsy. Then the custom spread to London, and New York where the fad really took off. Everyone and their uncle had a cat.
The current iteration of the U.S. Flag has been designed by a high school student
While the common opinions seems to be that American English in its current form was a result of simplification of British English of the time, a lot of the differences today are due to changes that British English underwent in the past four hundred years.
I think that modern mass culture, the defining characteristic of the Twentieth Century, traces its beginnings to the Great Depression.
Humans’ abandonment of the hunter-gatherer lifestyle — the invention of agriculture — is considered one of the most meaningful events in the history of mankind, giving rise of civilization and thus everything else. Specifically, agriculture increased the importance of land — suddenly the concept of ownership developed. Ownership necessitated the need to keep track of what belongs to whom, which led to accounting which led to writing which in turn led to higher, more abstract thought (and, yes, also poetry). But agriculture increased the importance of schedules which led to the idea of a calendar, which led to astronomy and then to mathematics. (However, the adoption of agriculture was not without its faults: there is some compelling archaeological evidence that we’re just now beginning to match our pre-agricultural ancestors’ average height and disease rate).
Finally, some claim that it is not the desire for efficiency that caused us to adopt agriculture, but the desire to brew alcohol. Beer, it is quite likely, may have led to human civilization.
A lot of Americans consider eating food very pleasurable, but — arguably — prior to Julia Child’s efforts, food had a much more utilitarian function in the American society.
We value financial success but that has not always been the case, as the pursuit of material comfort has its roots in Calvinism.