Atlas Shrugged is set in a dystopian United States at an unspecified time, in which the country has a "National Legislature" instead of Congress and a "Head of State" instead of President. Writer Edward Younkins noted, "The story may be simultaneously described as anachronistic and timeless. The pattern of industrial organization appears to be that of the late 1800s — the mood seems to be close to that of the depression-era 1930s. Both the social customs and the level of technology remind one of the 1950s". Many early 20th-century technologies are available, and the steel and railroad industries are especially significant; jet planes are described as a relatively new technology, and television is significantly less influential than radio. Although other countries are mentioned in passing, the Soviet Union, World War II, or the Cold War are not. The countries of the world are implied to be organized along vaguely Marxist lines, in references to "People's States" in Europe and South America. Characters also refer to nationalization of businesses in these "People's States", as well as in America. The "mixed economy" of the book's present is often contrasted with the "pure" capitalism of 19th century America, recalled as a lost Golden Age.
The novel is divided into three parts consisting of ten chapters each. Robert James Bidinotto noted, "the titles of the parts and chapters suggest multiple layers of meaning. The three parts, for example, are named in honor of Aristotle's laws of logic ... Part One is titled 'Non-Contradiction' ... Part Two, titled 'Either-Or' ... [and] Part Three is titled 'A Is A,' a reference to 'the Law of Identity'."
As the novel opens, protagonist Dagny Taggart, the Operating Vice President of Taggart Transcontinental, a railroad company established by her grandfather, attempts to keep the company alive against collectivism and statism. Her brother, James Taggart, the railroad's president, is peripherally aware of the company's troubles, but seems to make irrational decisions, such as preferring to buy steel from Orren Boyle's Associated Steel, rather than Hank Rearden's Rearden Steel, despite the former continually delaying delivery of vital rail. In this as in other decisions, Dagny simply continues her own policy, but is herself disappointed to discover that Francisco d'Anconia, her childhood friend and first love, appears to be destroying his family's international copper company without cause.
Hank Rearden, a self-made steel magnate, has developed an alloy called Rearden Metal, now the most reliable metal in the world, but keeps its composition secret, sparking jealousy among competitors. As a result, pressure is put on Dagny to use conventional steel, but she refuses. Hank's career is hindered by his feelings of obligation to his wife, mother, and younger brother. Dagny also becomes acquainted with Wesley Mouch, a Washington lobbyist initially working for Rearden, whom he betrays, and later notices the nation's most capable business leaders abruptly disappearing, leaving their industries to failure. The most recent of these is Ellis Wyatt, the sole founder and supervisor of Wyatt Oil, who leaves his most successful oil well spewing petroleum and fire into the air (later named "Wyatt's Torch"). Each of these men remains absent despite a thorough search by politicians. While economic conditions worsen and government agencies enforce their control on successful businesses, the citizens are often heard repeating "Who is John Galt?", in response to questions to which the individual has no answer. It sarcastically means, "Don't ask important questions, because we don't have answers", or more broadly, "What's the point?" or "Why bother?".
Having demonstrated the reliability of Rearden Metal in a railroad line named after John Galt, Hank Rearden and Dagny Taggart become paramours, and later discover, amongst the ruins of an abandoned factory, an incomplete motor that transforms atmospheric static electricity into kinetic energy, of which they seek the inventor. Eventually, this search reveals the reason of business-leaders' disappearances, when Dagny pursues a scientist to 'Galt's Gulch', where the character John Galt is leading an organized "strike" of business leaders against the government.
Reluctant to forsake her railroad, Dagny leaves Galt's Gulch, but Galt follows Dagny to New York City, where he hacks into a national radio broadcast to deliver a long speech (70 pages in the first edition), to explain the novel's theme and Rand's Objectivism. As the government collapses, the authorities capture Galt, but he is rescued by his partisans, while New York City loses its electricity. The novel closes as Galt announces that they will later reorganize the world.