Ok so in 1997 there was 28 MLB teams.
There's 30 now.
So that means there's 2 new teams since then.
One of them is the Washington Nationals.
And the second my brain won't allow me to think of it.
Anybody know?

The Arizona Diamondbacks and Tampa Bay Devil Rays were added in 1998, along with the Brewers moving from the AL to the NL. This had the net effect of increasing the NL from 14 teams to 16.

The Washington Nationals are the former Montreal Expos, so they are not a "new" team.