re: One State Holding All Three Major Sports Titles

First baseball is not a major sport.

But using these 3 sports in your question , technically it really hasn't happened for South Carolina either..

If you look at it for a calendar year, if USC wins it... It's 2017 and baseball and football haven't been crowned.
2016 would have been Nova, CC, Clemson

If you look at it from a school year fall-spring
You have Clemson, USC, ??

Or to include CC. It would be Bama, Nova, CC

Now reigning champion would include all 3, but the reign will most likely change in a couple months....

But this is just being technically.... I don't count the fact they made up the Tiger Slam either, you can't just choose when to start the Slam in golf or Tennis it starts with the first Slam of that calendar year.

However I think the state of South Carolina should be extremely proud and their teams sir have given their fans one hell of a ride.