The American System was championed by Henry Clay as a way to make the United States self-sufficient. Under the system, the industrial North would produce the nation's goods while the South and West would produce the nation's cotton and foodstuffs. In order to maintain this system, the federal government would undertake the construction of railroads and canals in order to connect markets. All of this would be paid for by a national bank that was fed with high tariffs in order to protect American manufacturers. The system was designed to improve the US economy and make the US more independent from market swings internationally.
Whigs such as Clay endorsed this system. They saw the federal government's role of stimulating the economy as vital. Democrats, on the other hand, believed in limited federal government. They did not see it as the federal government's role to be involved in infrastructure projects; rather, that was the job of the states. They saw a national bank as only increasing the political and economic clout of businessmen in the Northeast. Democrats also believed that agricultural areas would suffer by paying higher prices due to tariffs. Some Democrats also believed that Clay's system would only benefit him since it would appear as though he was responsible for creating the infrastructure projects. This could potentially allow Clay to poll well nationally and get him the presidency.