In The Lord of the Rings: Return of the King, Éowyn asks Aragorn his age and is shocked to learn that he is actually 87 despite looking no older than 40. But it is revealed that Aragorn is one of the Dúnedain—a descendant of Númenor—blessed with long life. Éowyn is in disbelief because it is said that Aragorn’s race had passed into legend. Aragorn says there are very few Númenóreans left by the time of the War of the Ring.
In The Lord of the Rings, the Númenóreans were descendants of the Edain, which was a group of Men that was considered the noblest of any group in the race of Men in the First Age. From the start of the Second Age, the Edain were gifted the island of Númenor by the Valar. The Edain were given this gift as a reward for assisting in the War of Wrath. In addition to being given an island to call home, the Edain were also given long life, greater height, and more intelligence. On average, this race would live to be at least 300. Once on the island, Elrond’s brother became the first king of Edain.
Elrond and his brother were half-elf, so they were given the choice to be mortal Men or immortal Elves. Elrond chose to be Elf, but his brother chose to be a Man. Unlike a normal Man, the Númenóreans aged very slowly. And instead of dying from sickness and in pain, once they felt their lives were nearing the end, the Númenóreans were simply able to lie down and peacefully drift away. In the Second Age, the king of Númenor was seduced by Sauron into attacking the Undying Lands. As a divine punishment, Eru Ilúvatar (also known as The One, who was the singular creator of all in existence) completely and utterly destroyed the island. The king’s actions led to the deaths of almost everyone on the island.
A great wave washed away the city and devoured its people. Nine ships were able to make a getaway, carrying the remaining Dúnedain to northern Middle Earth where they founded Gondor and Arnor. Gondor was a city founded by Isildur and Anárion. It was a very powerful city with a great and large military, but because of civil war between the people in the city combined with attacks from Sauron’s allies and a deadly plague, the city of Gondor slowly declined over the years until Aragorn was crowned king in the Third Age after Sauron’s defeat. With Aragorn ruling over Gondor, the city’s power became strong again, and the sister kingdom of Arnor joined forces under one leader with a new banner that claimed the land now be called Reunited Kingdom.
Aragorn II Elessar was the last descendant of Anárion. The line of kings of Gondor all came from Anárion, while the line of kings for Arnor were descendants of Isildur. When Aragorn was an infant of two years old, his father was killed by Orcs. Aragorn’s mother feared Aragorn would be killed (just like both his father and grandfather) if anyone were to find out who he was or that he was an Heir of Isildur, so she asked Elrond to take care of Aragorn in Rivendell and keep his lineage a secret. Elrond gave Aragorn a new identity by calling him Estel. It wasn’t until Aragorn was twenty years old when Elrond finally revealed his identity to him and told him of his ancestry. At this time, Elrond also gave Aragorn the Shards of Narsil as well as the Ring of Barahir—the ring with two serpents and eyes made of green jewels that Gríma Wormtongue spoke of in The Two Towers.
Around this time (age twenty), Aragorn also met and fell in love with Arwen. Arwen had been in Lothlórien, which was her mother’s original homeland, visiting her grandmother—Galadriel. Sometime after this, Aragorn left Rivendell to live in the wild amongst his remaining people called the Rangers of the North. Aragorn was in his twenties when he met Gandalf the Grey, and the pair quickly became good friends. Gandalf said Aragorn should monitor The Shire and the Hobbits that lived there, and he stayed just outside the borders and became known as Strider. During his time as a Ranger, Aragorn would provide morale to the armies of the West in an attempt to help keep the growing threat of Sauron at bay. But he maintained a low profile, using the name Thorongil and gaining skills as a fighter that he would use in the War of the Ring.
Aragorn was almost fifty years old when he once again met with Arwen in Lothlórien where he gave to her the Ring of Barahir. After this, Arwen vowed to marry Aragorn while also rejecting her Elvish lineage. Because she was half Elf like her father, Arwen chose to accept the Gift of Men—the gift being mortality and death. Some time passed, and Aragorn went East. During the War of the Ring, an Elf named Gildor Inglorion warned Aragorn the Ringwraiths were looking for him and that Gandalf was missing. Aragorn followed the Hobbits after they met Tom Bombadil and ended up in Bree, which is shown in The Lord of the Rings: The Fellowship of the Ring.