Most all wars are good for the economy in that it creates jobs for people that are not fighting the war. It also created work for factories in that they had to gear up and produce goods to be used in fighting the war.
We were heavily industrialized by the war, to a much higher degree than before. The war was incredibly expensive, so taxes were high (most people ave forgotten this) and key industries such as automaking and oil refining were taken over and run by the US government. Rationing was necessary, so ordinary American citizens had to do without a whole range of items, from new cars, to gasoline, to sugar, to tires.
Also economically, the war got the US permanently out of the Depression, when the New Deal had failed to do so on its own.
It is generally agreed that World War 2 provided a major stimulus to the American economy, starting a boom that has continued, with intermittent setbacks, till the beginning of the current depression. Various elements of the New Deal that had experienced only limited success during the 1930s really came to fruition with the war as demand from Europe and other theatres of conflict increased. Armaments are an obvious example but electrics and electronics as well as shipping, steel, food and agriculture and many other industries prospered too, and at the end of the war America was virtually alone among the major nations in having an economy that was not only intact but ready to drive the rest of the world back into economic health. Check out sites such as wikipedia and many others by googling american economy + world war 2.
What he said, although it should be noted that this was a completely unique situation in history. The fact that our industrial base was involved for years (through Lend Lease and its predesessor) before our armed forces were, built up our economy and industries to a degree no other nation had achieved. We supported the Chinese for five years before we entered the war, and the European Allies from '39 although we had almost no troops involved there until '43 (Africa) and '44 (D-Day). This and the financial juggling done to create the lease part of lend-lease allowed the US to get through the war with our economy intact and in position to keep growing while financing the rebuilding of other nations. This is, as far as I'm aware, the only major war in history in which a postwar boom occured, instead of a postwar depression.