Md. Code, Local Government § 9–109

(a) This section does not apply if the boundary between counties is a

navigable river.

(b) (1) Except as provided in paragraph (2) of this subsection, the

jurisdiction of a county bounded at any point by navigable waters extends from the

shore to the inside of the channel, which is considered the center of the waters.

(2) If the navigable waters join a neighboring state, the jurisdiction

of the county continues to the ultimate limit of the state.

(c) (1) The center of waters in subsection (b) of this section shall be as

represented on the county maps issued under the authority of Chapter 51, Acts of

1896 and Chapter 129, Acts of 1898.

(2) A county map referred to in paragraph (1) of this subsection is

admissible as evidence of the location of county boundaries.

(d) (1) Certified copies of county maps issued under subsection (c)(1) of

this section shall be kept on file with:

(i) the clerk of the court for each county; and

(ii) the governing body of each county.

(2) Certified copies of county maps are official and authoritative.

(e) Nothing in this section changes the rights the State may have on or

under the waters described in this section.