Because they started putting more money into the military funding.
American shipping was curtailed by the war which severely hurt the northern economy.
it doesnt
The war was costly financially and physically.
seven years war
The answer to that is going to depend a great deal on which area you have in mind.
it caused inflation, prices rose 9,000 percent %
Initially it increases the manufacturing base to provide the tools and equipment necessary for war to be conducted. Eventually as the costs increase the balance shifts and starts to hurt the economy.
WW2 not only didn't hurt the US's economy, it actually pulled us out of the Great Depression.
Why did a slowdown in railroad construction hurt the economy
war can hurt our economy because we need to repair if any country attacks us, also because we don't have the defense. but being neutral also means that we are less likely to be attacked and so we don't spend money on warfare.
Economy
The South had developed a more balanced economy after Reconstruction