True or False. Most historians today still support and even celebrate Frederick Jackson Turner’s “frontier thesis”

Answer 1

False, especially if by "most historians" you mean "historians who specialize in the study of the American West." Useful summary of post-Turner perspectives here: https://www.nytimes.com/1992/09/20/books/the-western-historians-don-t-fence-them-in.html. Cronon et al, Under an Open Sky (1992) is a good overview of the more complex approaches to the topic that supplanted Turner's "frontier thesis" and have shaped 21st-century scholarship in the field.