Maryland Code, Local Government § 21-626

(a) Property owned by the State or a unit of State government, a county, a municipality, or a regularly organized volunteer fire department that is used for public purposes is exempt from the taxes, user charges, and utility fees imposed under this part.

(b) Property that is not in a stormwater management district or is not otherwise provided direct or indirect stormwater management services in a stormwater management district may not have a tax imposed by the county until the county acquires, extends, or begins to provide stormwater management services, facilities, or programs to the property.