King Thingol was an elf of much influence living in Beleriand during the first age, even before the Noldor elves came from across the sea. I believe he was married to Melian the Maia, ruled the kingdom of Nargothrond which was enclosed in a magical barrier, and was the father of Luthien Tinuviel. I am uncertain what the elves who were left behind in Middle-earth when the Noldor and Teleri had left for Valinor, though Thingol was probably of the Sindarin elves.
Edit: I am wrong on some counts, right on others. Most of the inconsistency is in names, though there are some other chronology issues in my answer. All in all pretty good I would say.