Dagny is the heroine and primary narrator of the story. Her great stature comes from the combination of characteristics that she possesses. Her knowledge of engineering and industry enables her to expertly run a transcontinental railroad. Her understanding of physics allows her to identify the virtues of Rearden Metal. The independence of her judgment lets her stand by the metal and her railroad in the face of virtually unanimous social opposition. Her dauntless determination drives her to build the John Galt Line. The qualities that make Dagny a towering character are the same qualities that make real-life individuals such as the scientist Marie Curie and the innovative educator Maria Montessori great heroines. Like these women, Dagny has an unswerving dedication to truth, regardless of social opinion. The dedication to truth supports her ability to discover new knowledge and create new products.
The same attributes that make Dagny great also make John Galt great — and Aristotle, Michangelo, Leonardo da Vinci, and Isaac Newton. Rand dramatizes a crucial point in Dagny's character: Human greatness equals rational achievement irrespective of gender. Great human beings employ their intellectual ability to create the values on which human life depends. Stature of character is not gender-specific.
A reader may question why Rand portrays Dagny as an engineer — as a genius specifically in the field of heavy industry. If Rand's purpose is to portray a woman's intellectual prowess — to show that a gender-based difference between a woman's cognitive functioning and a man's doesn't exist — why not present her as a great writer, mathematician, theoretical scientist, composer, or artist? Why does she portray her as a brilliantly creative industrialist? In addition to the relevant plot considerations, Dagny's career path makes a philosophical point: If intellect is more life-giving than brawn, then women can run machinery, create new physical products, invent, innovate, oversee heavy industry, raise the material standard of living, and so on. The human intellect, regardless of gender, shapes the physical environment in order to meet human survival requirements. Ayn Rand doesn't believe that faith can move mountains. However, in the character of Dagny Taggart, Rand shows that a rational woman can create and deploy the technology to move mountains just as effectively as a rational man.
Like Galt, Dagny is much more than a pure intellect. Her emotional life is equally as intense as Galt's, and for the same reason. The men of the mind value man's life on earth; they love the industry, technology, and science that promote life. They feel enormous admiration and attraction for the giants among mankind who are responsible for progress. This admiration and attraction is why Dagny falls to her hands and knees, dirty and disheveled, shaking with excitement and screaming for Rearden, when she realizes the nature of the abandoned scrap of a motor she finds in a junk pile. This same admiration and attraction is why her body aches with a desire for Galt that verges on physical pain when she is in his home in the valley, and is why she races desperately back to New York when she hears the news of the Taggart Tunnel disaster. Dagny has committed mind, body, and soul to man's life on earth — and to the achievements and achievers that make life on earth possible.