According to the official 150th Anniversary Re-enactment site, this:
We now have officially gone over the 9,500 Reenactor mark with several hundred more registrations waiting to be entered, and 135 cannons and 375 horses. We have Reenactors registered from 16 different countries and all fifty states.
Accordingly, you may freak out. Yes, this is awesome. 135 canon?! Have you heard 135 canon going off? Over 9500 re-enactors? No one should miss this.