well, it created more jobs for people. (especially women) and factories and other businesses changed their production to war related items. i would assume that the economy wasnt horrible because the US was shipping war supplies to other countries early on which would result in money.
oh, and agricultural.... a lot of farms werent supplying as many goods to americans because their focus was concentrated on producing weapons, etc. the victory gardens (where people planted and harvest their own goods) was extremely popular during WWII.
if you dont have an AP US history study book i would defininlty recommend on getting one. they are life savers.