FreeCol

FreeCol is a clone of the classic Colonization and is strongly geared to Civilization. Your task is to start populating America in 1492nd. For this purpose, you start with one ship and two settlers. With the aid of the ship, you can trade with Europe and attract new settlers to America.
Of course they also come in contact with Native Americans and have to decide whether you want to live together peacefully or not.
As single player you can choose from four different nations. FreeCol also provides a multiplayer mode.