Thanks, Helena. I think you might be interested in the chapter of the book from which its drawn that addresses Turner—and how his frontier thesis was based on audaciously fraudulent statistics pushed by immigration restrictionists, trying to convince Americans the country had no room.
No further proof is needed that Turner viewed the conquest of America through the eyes of the colonizers. Still, his thesis that the waves of migration that carried "the nation" from the Atlantic to the Pacific could be explained by the sequential opening of govt land to private ownership remains.