So did I intially, so I researched it.
It wasnt from a casino anyway.
Liston vs Clay, November 1965, Las Vegas Convention Center looks like the 1st worldwide TV broadcast from Nevada (live anyway)

Now, not that I can remember as I was 3 years old, but it was a big thing even over here. I know my late father stayed up until 5 a.m. to watch it.

Anyone know what the first worldwide broadcast (from anywhere) in color was??