Vehicles must be parked parallel to a curb
Maryland Code, Transportation § 21-1004 (a) Except as otherwise provided in this section, a vehicle that is stopped or parked on a two-way roadway shall be stopped or parked parallel to the right hand curb or edge of the roadway, with its right hand wheels within 12 inches of that curb or edge of the roadway.

Vehicles cannot park next to a stop sign
MD Code, Transportation, § 21-1003, section O (2) A person may not stand or park a vehicle within 20 feet of a crosswalk at an intersection. Standing or parking vehicle near approach to signals or signs
(o) A person may not stand or park a vehicle within 30 feet on the approach to any flashing signal, stop sign, yield sign, or traffic control signal located at the side of a roadway.

Vehicles cannot park in front of a fire hydrant.
MD Code, Transportation, § 21-1003 (m) A person may not stand or park a vehicle within 15 feet of a fire hydrant.

Other notable community parking restrictions
(c) A person may not stop, stand, or park a vehicle on a sidewalk.
(j) A person may not stop, stand, or park a vehicle at any place where stopping is prohibited by an official sign.