Why isn't Portugal part of Spain?

I haven't done any research on this, but I've always wondered why Portugal is a separate country and isn't part of Spain. It even has it's own language but it is sitting there, almost the entire western expanse opening on the the Atlantic Ocean. Wouldn't Spain want all of its ports? My theory is that the coastal cultural has been extremely different from that of the interior. My guess is that the Portuguese were more settled along the coast, while the masses on the rest of the Iberian Peninsula were still tribal nomads. And were able to defend themselves again the various warring provinces of what is now Spain. But then after 1492, Spain took over most of the new world and would have taken England except that the weather in the Channel was so bad their armada sank. Spain does have its Atlantic ports too, its access to the sea and trading routes. Perhaps, the larger number of people in Spain, which was largely consolidated by Queen Isabella and King Ferdinand.

I've come to this conclusion after sitting in a Benihana booth, squeezed in actually, with two men in their late 50s or early 60s from Knoxville, Tennessee. They seemed to be from another planet: slow, deaf, drinking a lot, scarfing down the Japanese food with a fork, interacting with the wait-staff as if they were from another species. They got me thinking about the strips of sophistication we have along our coasts. New York State and California (particularly California)could feed themselves if need be. Will have to read the history of Portugal.

The Benihana, the "longest running dinner show in the world" they claim, is not my favorite restaurent on earth. They don't throw knives around any more, just spatulas and spoons. Fear of liability suits. I wonder if anyone was ever hurt by the flying knives. The "show" is boring and food mediocre. Now around 1976 in Rochester, New York, we went to our first Benihana, where the chef did throw knives. After the knife show while chef is preparing the food, my father has to strike up a converation with him. "So, where are you from?" my father asks, everyone his buddy, everyone a potential admirer and member of my father's audience. "Heroshima," was the response. No more talking to the man with the knives and good aim.