A modern definition of the border initially claimed by Spain begins at the mouth of Calcasieu Pass on the Gulf of Mexico (coord), thence up the Calcasieu River to its source (coord), thence due north (along meridian 93°12'47"W) to the Red River (coord), thence up the Red River to the meridian (99°15′19″W) of the source of the Medina River (coord), thence due north along that meridian (99°15′19″W) to the Arkansas River (coord), thence up the Arkansas River to its source (coord), thence due west (a distance of about 12 kilometers along the parallel 39°15'30"N) to the Continental Divide (coord), thence northward along the Continental Divide presumably all the way to the Bering Strait.