As a member of the United States Exploring Expedition, he had visited the Pacific Northwest in 1841.

Missionary Marcus Whitman was credited for providing "much valuable information" about the Cayuse people and other natives nearby Waiilatpu.

[7] Bruce Rigsby reexamined the Cayuse-Molala lexical pairs provided by Hale in 1969 and found only a tenth to be potentially related terms.

Upon his review of extant Molala and Cayuse linguistic data, Rigsby concluded "I do not see how the two languages could have possibly been mutually intelligible.

Their Cayuse informants had highly limited knowledge of the language and were more fluent in either Sahaptin or Nez Perce.