Miss. Code Ann. § 19-1-59

Jackson County is bounded by beginning at the northwest corner of section three, township four, south, range nine west; thence due south through the middle of said range nine to middle of the Bay of Biloxi, thence along the middle of said Bay of Biloxi to its entrance at the east end of Deer Island; thence due south to the southern boundary of the State of Mississippi on the Gulf of Mexico; thence eastwardly along said boundary, including all the islands within six leagues of the shore of the Gulf of Mexico, to the boundary lines between the States of Alabama and Mississippi, thence northwardly along the said boundary line to the point where the township line between townships three and four, south, intersect said state boundary line; thence west along said township line between townships three and four, south, to the point of beginning. The county site is Pascagoula.