+1 on the Marriottsville Muzzleloaders, if you are up Baltimore way. Not sure there is anything else in Maryland as such, I'd look at Virginia and Pennsylvania. There's a F&I war reenactment at Fort Frederick State Park (https://friendsoffortfrederick.info/calendar.html).
I belonged to a club in PA back in the 80s and they used to have a blackpowder shoot ever month. I Was a bunch of fun. Wish there was something similar in the area. I did hear there is a place in King George County Va that holds one