Who began writing the Red Book of Westmarch?

Bilbo Baggins began writing the Red Book of Westmarch. It started as a personal record of his journey to Erebor, later known as There and Back Again, A Hobbit’s Holiday.

Bilbo expanded the account during his retirement in Rivendell, recording not only his own adventure but also material about Frodo’s quest and the War of the Ring. He left his diary, notes and other writings to Frodo, who organized and wrote most of the account covering the events of The Lord of the Rings.

Frodo was close to finishing the book when he left the final pages for Samwise Gamgee. Sam therefore continued the manuscript, but he did not begin it. Later copies and additions helped create the version known as the Red Book of Westmarch, named for its red binding and its association with the Westmarch of the Shire. Merry and Pippin contributed learning and records elsewhere, but neither started the Red Book.