I think everyone agrees that "early" members of the Church believed the American Indians in the U.S. and its territories were Lamanites. Here, Oliver refers to the Delaware Indians as the "deleware Nation of Lamanites."
That fits pretty well with what the Lord said in D&C 28, 30 and 32.
Here is a short history of the Delaware nation:
Among other things, Oliver wrote:
"I this day received heard from the deleware Nation of Lamanites by the man who is employed by government a smith for that Nation he believes the truth and says he tha[n]ks God he does believe and also says that he shall shortly be baptized which I pray God may be the case for truly my brethren he is a man he also says that we have put more into the lamenites during the short time we we were permited to be with them (which was but a few days[)] then all the devels in the infernal pit and and and all the men on earth can get out of them in four generations he tells me that, that evry Nation have now the name of Nephy who is the son of Nephi & handed down to this very generation, there is only a part of that Nation here now but the remainder are expected this spring the principle chief says he believes evry word of the Book & there are many <more> in the Nation who believe and we understand there are many among the Shawnees who also believe & we trust that when the Lord shall open the <our> way we shall have glorious times for truly my brethren my heart sorrows for them for they are cast out & dispised and know not the God in whom they should trust we have traveld about in this country considerable and proclaimed repentence and very <many> are very anxious serious & honest."
You can see the entire letter here: