Why did Stalin blockade Berlin? How did the United States respond, and what resulted?

In 1948, Stalin was upset with the 'occupational zones' (Soviet east zone - US, UK, French west zone) set up in Berlin. He expected that blockading the city from western supplies would cause the western Allies to give Soviet's control of the city. The U. S refused, and the Berlin Airlift ensued, in which allied bombers flew over 600 tons of food a day into Berlin, the Soviets soon saw the blockade wasn't working, and lifted it, after being publicly humiliated over the total failure of the blockade.