How could anyone have a "Cold Beer" in the USA, prior to the 1870s?

Watch any TV Western or movie about the “Old West,” and you’ll invariably see some cowboy walk into a saloon and plunk down 5¢ to have a cold beer.

OK, just HOW did that beer get cold?

Electricity was developed commercially by Thomas Edison in 1879, with his perfection of the electric light, and commercial air conditioning, followed much later, obviously.

So how were those “Old West” saloons of the 1800s (other than during the cold winter months, of course) able to supply cold drinks, with no electricity?