Timucua
Timucua is a language isolate once spoken across northern and central Florida and into southern Georgia, where it was the principal native tongue at the time of Spanish colonization. Its nine or ten dialects differed only slightly and served mainly to mark tribal boundaries.
Nearly everything known of the language comes from Francisco Pareja, a Franciscan missionary who reached St. Augustine in 1595. He devised a writing system and between 1612 and 1628 printed Spanish-Timucua catechisms and the first grammar.
The speech of the Calusa and Tocobaga on the Gulf coast was almost never written down and remains unclassified. In 1763, when Spain ceded Florida to Britain after the Seven Years' War, the last Timucua speakers left with the Spanish missions for Cuba and the language fell silent.