Check out photographs of turn-of-the-century New York City, and you see all these crowd shots that are just an endless sea of hats. Bowlers, fedoras, flat caps. As far as the eye can see, everyone's wearing a hat.

Nowadays you see baseball caps here and there, maybe a cowboy hat if you're down in Texas. But the days of everyone wearing a hat are long gone. If you see someone in a fedora these days, they stick out like a sore thumb. So, what happened? Why did American men slowly phase out the hat through the first half of the 20th Century?

This shift actually comes down to a few different changes in American lifestyles. First of all, more people were working indoors after the Industrial Revolution. If you're not out in the sun all day, then a hat is just dead weight you have to carry around. Plus, people were driving cars or taking buses and trains to work, so they didn't need to worry about sun and rain on the way to and from the job, either.

But if we're talking fashion history, it really comes down to the movies.

Even before cars and factory jobs rendered hats impractical, actors in films would generally go hatless because a round-brimmed hat would obscure their face on camera. Americans have always taken their fashion cues from movies and television (think back on how popular black clothes and sunglasses were right after The Matrix came out), so when we saw Rudolph Valentino and Lon Chaney going hatless more often than not, that normalized the idea, and more American men followed suit.

Eventually, hats were simply phased out, owing primarily, but not exclusively, to these factors.