This important document has disappear from the National Park Service website. This is the broken link. I was able to retrieve it using the Wayback Machine on Archive.org. It was available as recently as May 2017.
Just so it stays hosted the web, I’m archiving on my site. Copy of Speech. (pdf format)
If you are interested in this speech you may also be interested in the journals from the same time.
Liv Mariah Yarrow 
[…] I also want to think about the possible influence of the Bingham version of the speech on the Lewis speech to the Yankton Sioux! Note especially the use of the FAMILIAL […]