The 3MC Texas Aggie Muster to be held in Mason on Thursday, April 21, 2016, at 6:00 p.m. Each year Aggies throughout the world join together to celebrate Muster and this year, Mason will host the Muster event for Menard, Mason, McCulloch, and Concho Counties. Muster is a day celebrating the camaraderie and the friendships, the triumphs and the defeats, the legacies and the impact that Texas A&M University has made, and continues to make, in all of our lives.