A number of languages of North America are too poorly attested to classify.
These include Adai, Beothuk, Calusa, Cayuse, Karankawa, and Solano.
There are other languages which are scarcely attested at all.
Lyle Campbell et al. (2007) list the following extinct and nearly unattested language varieties of North America as unclassifiable due to lack of data.
† Ethnographic evidence suggests these varieties might have been Uto-Aztecan.