Dear Mr. Wandschneider,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located Letters Received, 1824 - 1880 (M234) in the Records of the Bureau of Indian Affairs (Record Group 75) that contains 38 references to the Nez Perce during the 1850s and 1860s. This correspondence may include information about the treaties that you seek. These records have been digitized and are available for viewing via the Catalog.
We also located the series Indian Treaties, 1789 - 1869 in the General Records of the United States Government (Record Group 11) that includes documents of and about the 1855 Treaty, the October 1855 Treaty and the 1863 Treaty. These records have been digitized and are available for viewing via the Catalog.
Additional information may be located in the Native American Indian Law Research Guide: Treaties at Marquette University Law School Eckstein Library and by contacting the National Museum of the American Indian (NMAI) Archive Center at firstname.lastname@example.org.
We hope this is helpful. Best of luck with your research!