The number of available workers and, more importantly, their productivity help determine the health of the U.S. economy. Throughout its history, the United States has experienced steady growth in the labor force, a phenomenon both cause and effect of almost constant economic expansion. Until shortly after World War I, most workers were immigrants from Europe, their immediate descendants, or African Americans who were mostly slaves taken from Africa, or slave descendants. Beginning in the early 20th century, many Latin Americans immigrated; followed by large numbers of Asians following removal of nation-origin based immigration quotas. The promise of high wages brings many highly skilled workers from around the world to the United States.

Labor mobility has also been important to the capacity of the American economy to adapt to changing conditions. When immigrants flooded labor markets on the East Coast, many workers moved inland, often to farmland waiting to be tilled. Similarly, economic opportunities in industrial, northern cities attracted black Americans from southern farms in the first half of the 20th century.

In the United States, the corporation has emerged as an association of owners, known as stockholders, who form a business enterprise governed by a complex set of rules and customs. Brought on by the process of mass production, corporations such as General Electric have been instrumental in shaping the United States. Through the stock market, American banks and investors have grown their economy by investing and withdrawing capital from profitable corporations. Today in the era of globalization American investors and corporations have influence all over the world. The American government has also been instrumental in investing in the economy, in areas such as providing cheap electricity (such as from the Hoover Dam), and military contracts in times of war.

While consumers and producers make most decisions that mold the economy, government activities have a powerful effect on the U.S. economy in at least four areas. Strong government regulation in the U.S. economy started in the early 1900s with the rise of the Progressive Movement; prior to this the government promoted economic growth through protective tariffs and subsidies to industry, built infrastructure, and established banking policies, including the gold standard, to encourage savings and investment in productive enterprises.