Mary Anne first started putting together staff for the magazine that became Strange Horizons back around January of 2000, but it wasn't until mid-May that she publicly announced that the magazine would be happening; ten years ago today.
A couple of days later, she gave more info about the motivations and (then-tentative) plans.
We didn't launch until September 1, 2000, so still three and a half months to go 'til the tenth anniversary of the launch. But I figured it was worth noting today as a partial anniversary of a sort.
Another anniversary will come in late June: our very first fiction submission arrived on June 27, 2000.