While Frodo struggled with carrying the One Ring, Samwise Gamgee was the true reason for it made it to Mount Doom. He saved Frodo countless times from the clutches of death and even carried the Ring himself for a short time. But after all was said and done, the Fellowship parted ways, and Frodo set off into the Undying Lands, leaving Samwise to start a new journey after the events of The Lord of the Rings.
While The Lord of the Rings: The Return of the King ended shortly after Sauron's defeat, author J. R. R Tolkien expanded the lore around almost every major character. And through the books' appendices and Tolkien's other pieced-together writings, it's known what ultimately became of Samwise and his family that followed.
While Peter Jackson's movie adaptation showed Hobbiton untouched from the war, the book version was not so lucky. Upon the Hobbits' return, they were met by an enslaved and industrialized Shire, which they had to wage war over to liberate. But after the ruffians were dealt with, and Saruman was killed on the steps of Frodo's house, the Hobbits were finally able to settle down.
However, when Frodo left for the West, he gifted Sam his house under the hill -- Bag End, a home that had been in the Baggins family for generations but was left with no more heirs. Sam accepted this gift and moved in with his newly wedded wife, Rosie Cotton. But before being able to fully rest, Samwise put his gardening skills to work and helped restore much of the Shire which was ravaged by war.
Sam and Rosie went on to bear 13 children, which was common for Shire-folk, and the Gamgee family was so well-known for restoring the surrounding nature that they were referred to as the Gardeners of the Hill, which pushed Sam into accepting Gardener as their new surname. And that reputation carried Samwise far, as he later ran for Mayor of the Shire and won.
His role as mayor lasted for a long 42 years before he resigned, and the Shire prospered all throughout. But eventually, Sam grew old, and his wife passed away from old age. At that point, he passed down Bag End to his children and decided to head West, just like Frodo did 50 years before. Since Sam was a ring bearer for a brief time, he was granted passage into the Undying Lands, and he crossed over to once again reunite with Frodo.
Nothing is known about Samwise's fate, or what the Undying Lands are even like, but it still feels like an appropriate end for the character. Unlike Frodo, the comforts of the Shire never left Sam, and his adventures gave him the confidence to marry Rosie and move beyond a simple gardener.