Anarion was a Dunadan and the younger son of Elendil the Tall. With his brother, Isildur, he was the second King of Gondor. When he left Numenor with his father, Elendil, and his brother, Isildur, he owned two of the nine ships of the Faithful. When they came to the shore of Lindon, Elendil founded the realm of Arnor, and Isildur and Anarion bore south to what is now Gondor. Two strong places they built, one in the west and one in the east. Anarion's home was Minas Anor, Tower of the Setting Sun, and Isildur's home was Minas Ithil, Tower of the Rising Moon.
Also, the Palantiri were divided. Anarion and Isildur took two each and placed them in Orthanc, Minas Anor, Minas Ithil, and Osgiliath.
Soon, Sauron prepared for war. First he took Minas Ithil, and destroyed the white tree of Isildur. But Isildur escaped down the Anduin, seeking Elendil. Meanwhile, Anarion defended Osgiliath.
Gil-galad and Elendil took counsel, and the Last Alliance was formed. Anarion joined the march to Mordor, but was slain by a rock thrown from Barad-dur. His helm was crushed and so the helm of Isildur was used as the Crown of Gondor from then on.