Karankawa is an extinct language of the East Texas coast. The language has not been spoken since the 1850's.
Karankawa is generally considered a language isolate (a language unrelated to any other known language), though some linguists have tried
to link it to the Coahuiltecan, Hokan,
or even Carib language families.
Since few records of the language remain and those records contain many discrepancies, this question will probably never be answered
conclusively.
The Karankawa Indians
Overview of Karankawa history, with different records of European interactions with the Karankawas.
Texas Indian Maps:
Tribal map showing the original territory of the Karankawa Indians and their neighbors.
Karankawa Indians
Article on Karankawa history and culture from the Handbook of Texas Online.
Karankawa Indian Tribe
History and genealogy of the Karankawa Indians.
Written In Smoke
Article on the Karankawa tribe and their little-known culture.
The Karankawa
Essay on the Karankawas of Texas.
Karankawa
Wikipedia article on the Karankawa tribe.
Karankawa Tribe
Karankawa links.