Slipknot have announced the lineup for their Iowa show celebrating their 25th anniversary of Knotfest. Along with Slipknot, Knocked Loose, Hatebreed, Poison The Well, GWAR, Zulu, Dying Wish, Twin Temple, Vended, Holy Wars, Swollen Teeth, Till Lindemann, Spine, and Dose will be playing the show. Knotfest Iowa will take place at Water Works Park in Des Moines on September 21.