I live between Baltimore and Washington, D.C. so I can offer a few in my area, but it is a big state.
Columbia, MD - P.U.P.S. with Karen Decker. She was recommended to me by Theresa Currier, a worlds IPO and National PSA competitor. I personally haven't trained with Karen Decker, but I hear good things.
Elkridge, MD - Tecla's K-9 Academy. It's a little pricey, but I enjoyed what I learned. I've done Puppy classes, Rally, Nosework, and Competition Obedience (for IPO/IGP) there.
Glen Burnie, MD - Dauntless Dogs. I trained my shiba with the owner of this group. A balanced trainer. They do a lot of basic obedience and some more advanced stuff. I know people happy with their training as it's more in line for pets, but I was looking for more with my other two and went elsewhere.
There's a local dog training club I'm currently going to for the lower prices called Oriole Dog Training Club in Halethorpe, MD. The trainers are varied and it's all volunteer based. I'm taking intro to Agility with my female here and took Conformation and puppy class here. They offer all sorts of training, but it's based on "seasonal" training. There's a short window to apply every 3 months. Some examples of classes - Nosework, Agility, Conformation, Rally/Obedience, pet obedience classes, Flyball.
+ Kalbi CGC 6/21/2015
+ Blackthorn's Out of the Frying Pan NW1 ORT SEN SCN BCAT SIN RATN TKN (Katsu) 9/12/2017
+ Blackthorn's Skofnung CGC TKN RATI RATO (Steel) 07/23/2018