Jordan took the West Bank when the British Mandate was terminated. The international community had designated it to become part of the Jewish National Home. This is also why practically noone acknowledged Jordan's rule of the West Bank. Before 1946, Jordan itself was part of the British Mandate. It was separated to create a country where Arabs from the region could live, whereas Palestine would become the Jewish National Home. http://en.wikipedia.org/wiki/British_Mandate_of_Palestine#Te...
"Also, remind everyone, when was Israel created?"
About 1000 BCE. http://en.wikipedia.org/wiki/Kingdom_of_Israel_%28united_mon...
"isn't the article about Gaza at least partially also?"
Sure, and Gaza was part of the British Mandate as well. In 1922 it was designated to become part of the Jewish National Home. http://en.wikipedia.org/wiki/History_of_Gaza#British_Mandate...