The Gulf of Mexico did not exist 250 million years ago when there was but one supercontinent, Pangea . As Pangea split apart, the Atlantic Ocean and Gulf of Mexico opened. Louisiana slowly developed, over millions of years, from water into land, and from north to south.  The oldest rocks are exposed in the north, in areas such as the Kisatchie National Forest. The oldest rocks date back to the early Tertiary Era, some 60 million years ago. The history of the formation of these rocks can be found in D. Spearing's Roadside Geology of Louisiana . 
Louisiana ( French : La Louisiane; by 1879 [?], La Louisiane française ) or French Louisiana  was an administrative district of New France . Under French control 1682 to 1762 and 1802 (nominally) to 1803, the area was named in honor of King Louis XIV , by French explorer René-Robert Cavelier, Sieur de la Salle . It originally covered an expansive territory that included most of the drainage basin of the Mississippi River and stretched from the Great Lakes to the Gulf of Mexico and from the Appalachian Mountains to the Rocky Mountains .