when was the book by J.R.R. Tolkien that Bilbo Baggins is the title character and protagonist originally published?
Bilbo Baggins: Bilbo Baggins is the title character and protagonist of J. R. R. Tolkien's 1937 novel "The Hobbit", as well as a supporting character in "The Lord of the Rings". The Hobbit:  It was published on 21 September 1937 to wide critical acclaim, being nominated for the Carnegie Medal and awarded a prize from the "New York Herald Tribune" for best juvenile fiction.
21 September 1937