When Did the "Cocktail Hour" Become a Part of American Life?

I recall (as a child) visiting my Grandparents-and it seemed that they ate dinner pretty late (about 7:00 PM. Before that, they would have a drink-usually a whiskey sour or martini. They had a big chrome cocktail shaker, and a set of matching cocktail glasses. I was always fascinated by the ritual of making the drinks-mix the liquors (from fascinating bottles with colorful labels), add fruit juices, sugar, etc, ice, then shake everything in the big cocktail shaker-then pour.
When did this ritual become common?
Looking at the old “Thin Man” movies (Powell and Myrna Loy), they always seemed to be quaffing cocktails-was this a common ritual in American homes?

My WAG would be the 30s, after the repeal of prohibition . . . or perhaps the 20s, in speakeasies.
It certainly had become quite common by the 50s.

I think this is one old-fashioned thing that needs to make a comeback.

IIRC cocktails only became really popular in during Prohibition when speakeasies started using fruit juices & the like to try and coverup the tast of poor quality bootleg liquor.

And prohibition meant that people developed a taste for easily transported high-proof spirits, rather than beer.

Easily-transported and -stored distilled spirits were popular for those same reasons long before Prohibition.

However, it is true that many classic cocktail recipes were invented and/or popularized in the '20s.

The OED has a first cite from 1927.