Bilbo Baggins:

Born in the year 2890 of the Third Age, Bilbo was a bachelor, who was chosen by Gandalf to make up the lucky number for the Quest for Smaug's treasure in 2941. Needless to say, the Dwarves were not particularly amused with Gandalf's choice (thinking him more of the type of a grocer or some other tradesman) until Bilbo warned them of the crack in the wall of the goblins cave, rescued them from the spiders in Mirkwood, and freed them from the Woodelves. In the process of doing all this he found a magic ring which he used to help the Dwarves, though he kept it secret as long as he could. After he returned from his "holiday" as he often chose to call it, a year later, Bilbo settled down to write his diary, which we know under the following titles:

The Hobbit
The Hobbit, There and Back Again

In the year 3001, of the Third Age, and Bilbo's 111 birthday, he disappeared and left Bag End to Frodo Baggins, his nephew. After he disappeared, Bilbo traveled to Dale, and saw the changes the Dwarves had made, and then back to Rivendell where he stayed until after the War of the Ring when he sailed into the West with the Keepers of the Three Rings and Frodo, the other Ringbearer.

Bilbo wrote the early parts of the Lord of the Rings, which shows in the tone of the early parts of the tale. However, he gave it to Frodo to finish as he was getting too sleepy, as he said, and is recorded in the Lord of the Rings.