Md. Code, Real Property § 13–401

The following persons may file an objection to the granting of a patent for all or any portion of the land described in the application:

(1) Any person or governmental body with prior title to any portion of the land, except that, if the land is land for which a patent never has been issued, the State and its agencies may object only in accordance with item (3) of this section;

(2) Any person who possesses any portion of the land under claim of ownership in a manner that, either directly or by tacking, is actual, open, notorious, exclusive, and continuous and uninterrupted for the 20 years immediately preceding the date of filing the application; and

(3) The State or any agency of the State that requires any portion of the land for public purposes.