[Fingolfin II]

As mark12_30 said, Unfinished Tales is the way to go.

Briefly, I'll describe the story behind 'Dol Amroth'-

Basically, an elven-maiden named Mithrellas was a companion of Nimrodel, the love of Amroth. However, she got separated from Nimrodel and became lost in the woods of Belfalas, where she met a Numenorean named Imrazor. They had a son, Galador, who was a half-elf. He became the lord of Belfallas and the first Lord of Dol Amroth (named after Amroth, the ex-King of Lorien). Imrahil was descended from Galador.

Another interesting thing is that Boromir and Faramir have elven, as well as Numenorean, blood running through their veins as their mother is Finduilas, sister of Imrahil!