A bit of history that you might not know:
Maryland was a Confederate state that wasn't not allowed to join the Confederacy because of Federal Military occupation. Very much needed because of Washington, DC being SOUTH of Maryland.
The famous Federal Hill looking over Baltimore's Harbor used to have a federal fort on it with its guns aimed right across the harbor at the Maryland Club - a hotbed of Confederate sympathizers.
Federal troops taking trains from the north could not travel straight through Baltimore (because the trains and train tracks didn't match) They had to march a mile or two from the end of the northern tracks to reach the beginning of the southern tracks. These troops were often fired upon by the citizens of Baltimore.
(Things my father-in-law told me about his home town.)