system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was Las Vegas built in such miserable heat?

I just find it strange to built such a large and well known city in the desert where it can be as hot at 120°.
gpt
Las Vegas was a water stop on the Old Spanish Trail. The springs (which fed the meadows) created a rare oasis, and a pleasant one. For much of the year, Las Vegas has beautiful weather: mild sunny days, cool nights. That was traveling time.

The Old Spanish Trail connected the Pacific Coast ports with Santa Fe, the inland-northern top of Spain/Mexico's North American empire. It was a treacherous road west over the Mojave Desert, and Las Vegas was a full-service wagon-road stop. When railroads connected Salt Lake City and Los Angeles, Las Vegas was a natural place for a railway town with all the services rail travelers needed.

Because Arizona choose poorly in the Civil War, the area that is now Las Vegas in Clark County, NV, was taken from the northwest tip of Arizona. And that proximity to Los Angeles during the economic boom of the post-WWII era made it acceptably close to Los Angeles for a weekend of Sinatra and Ann Margaret and gambling over martinis.

—Former Nevadan here. (And one who greatly enjoyed the state's history!)