Capitalism: Since man survives by using his reasoning mind, he should be free to act upon his mind's own judgment--free to work on his own behalf, toward his own self-interest, for his own happiness. And the freedom to act must include the freedom to trade with other people, unfettered by anything other than other individuals' willingness to associate with him. That's capitalism.
Therefore, the Objectivist philosophy holds that capitalism--- pure, unobstructed, free markets--is the proper political/economic system conducive to the life of a rational being. From this standpoint, Objectivists oppose any government involvment into economic affairs (except in the case of literal physical force or fraud).
Note: What we have in America is not laissez faire (unrestricted) capitalism, as it should be, but rather a sort of mongrel-economy, containing some capitalism and some state controls.