Here's what the Washington State Library says about the Chief's speech: "The best description of the saga of Chief Seattle's speech can be found in an essay by Rudolf Kaiser: "Chief Seattle's Speech(es): American Origins and European Reception" published in Recovering the Word: Essays on Native American Literature by the University of California Press, 1987. Another excellent discussion appears in David Buerge's article "Seattle's King Arthur: How Chief Seattle continues to inspire his many admirers to put words in his mouth," appearing in the July 17, 1991 Seattle Weekly."
Chief Seattle's famous speech, whatever its contents, was not given in English. There is no accurate translation of his speech; indeed, there's no translation at all, just a number of fanciful attributions among which the most widely circulated are Smith's of 1887 and T. Perry's from 1971.
The Chief's gravesite in Washington State is worth a visit. Quiet, peaceful, environmentally intact surroundings, a dignified monument, and on the day I was there a nice assortment of offerings including a few packs of cigarettes, some bottles of beer, and additional gifts. Not exactly what we might associate with an early environmentalist, but there were no indications that the Chief objected. :-)