Also known as "Plains Sign Talk", "Hand Talk".
"Scholars dispute exactly when, in their 30,000-year history in North America, tribes developed sign language. It was observed among Florida tribes by 16th Century Spanish colonizers." .. "Hand Talk was also the first language of deaf Natives." "Native American Hand Talkers Fight to Keep Sign Language Alive". https://www.voanews.com/a/native-american-hand-talker-fight-to-keep-signed-language-alive/3794333.html
Native American sign language: Illustrated guides to 400 gestures. https://clickamericana.com/topics/culture-and-lifestyle/native-american-sign-language-1954
Mallery, Garrick. "The Project Gutenberg Ebook of Sign Language among North American Indians compared with that among other peoples and deaf-mutes." 1879-1880. http://www.gutenberg.org/files/17451/17451-h/17451-h.htm
Hidatsa Language and 100+ phrases with Plains Sign Language by Lanny Real Bird. https://www.youtube.com/watch?v=0LKM6iv4h4k
Scott PISL Dictionary by Major General Hugh Lenox Scott (1853 – 1934). https://www.youtube.com/watch?v=j8Il5R59sI4
The YouTube video ( https://www.youtube.com/watch?v=bfT2a5SGDFA ) shows an example of what Plains Indian Sign Language looked like in 1930 during the Indian Sign Language Conference in Browning, Montana, where Native American signers from 14 different Plains tribes participated in. The conference was sponsored by the U.S. government to demonstrate the Plains signed language and to preserve this ancient intertribal language by recording it on film.
"Hand Talk: Sign Language among American Indian Nations" (2010) by Jeffrey E. Davis, University of Tennessee. https://www.cambridge.org/gb/academic/subjects/languages-linguistics/sign-language/hand-talk-sign-language-among-american-indian-nations?format=HB&isbn=9780521870108
"Indian Sign Language" (1969) by William Tomkins. Available on amazon.com
"Plains Indian Sign Language: A Memorial to the Conference." http://ublib.buffalo.edu/libraries/e-resources/ebooks/records/7132.html
"Indian Sign Language." http://www.inquiry.net/outdoor/native/sign/index.htm (image-based dictionary)