Some say it started with Wrestlemania 13 though and Austin vs. Bret, but the "boom" business wise didn't get rolling 'til '98 for sure.
For me thats when the seed was set for sure. That iconic moment of Austin in the Sharpshooter. I just don't think WWE knew what to do with it for another 3 to 4 months. It and by that i mean Austin just snowballed and the rest is history.
Just an Incredible period for me.