In the 1940s the united states grew more than it had in the previous 40 years. as the united states became more industrialized and farmers shifted to specialization, the market revolution occurred and incomes rose. the increase pace of economic growth was most dependent on

During the 1940's the economic growth was rapid.  The country was recovering from the Great Depression in the late 1930's, so the events of the 1940's were a huge economic turning point for Americans.  The MOST significant of these events was World War II.  After the Japanese attack on Pearl Harbor on December 7, 1941 the United States was catapulted into an economic boom created by need for soldiers, warfare products and medical care.  

Young and able men went off to war in Europe and were compensated my the government for their service. Everyone else, including women, were recruited into working roles to support the men in uniform.  Factory workers created everything needed for the U.S. to come out victorious.  They made vehicles, uniforms, weaponry, ammunition, MRE's (meals ready to eat) and many other goods.  Others became medical professionals and went to hospitals and battle field medical tents to heal the wounded and sick soldiers.  

The increase in demand of goods made once small companies into major corporations and created massive amounts of jobs for a population that was desperately in need of employment.  Following the war and entering the Cold War Era, these corporations began to emerge into major conglomerates and start bringing their business international.  Other major consumer industries started to pop-up as well, such as McDonalds and car rental.  People were working and had money to spend so industries were flourishing. World War II had an enormous impact of the U.S. economy that lasted for decades to follow.