Spain: 1516-Present
Spain was formed in 1516, 24 years after the "Reconquista" (the Expelling of all Muslims in the Iberian Peninsula). The Kingdoms of Castile, Leon, and Aragon united under one banner when all three kingdoms were inherited by Carlos I and became one country for the very first time. Prior to 1516 there was one monarch for Castile and Leon, and a second monarch for Aragon. Carlos I was the grandson of both Isabel and Ferdinand when he inherited the kingdoms that had belonged to each, and their heirs, separately. That was what unified the three kingdoms.