Atlas Shrugged: Part I

It is 2016 and the United States is in a sustained economic depression. Industrial disasters, resource shortages, and gasoline at $37/gallon have made railroads the primary mode of transportation, but even they are in disrepair. After a major accident on the Rio Norte line of the Taggart Transcontinental railroad, CEO James Taggart shirks responsibility. His sister Dagny Taggart, Vice-President in Charge of Operation, defies him by replacing the aging track with new rails made of Rearden Metal, which is claimed to be lighter yet stronger than steel. Dagny meets with its inventor, Hank Rearden, and they negotiate a deal they both admit serves their respective self-interests.
Politician Wesley Mouchânominally Rearden's lobbyist in Washington, D.C.âis part of a crowd that views heads of industry as persons who must be broken or tamed. James Taggart uses political influence to ensure that Taggart Transcontinental is designated the exclusive railroad for the state of Colorado. Dagny is confronted by Ellis Wyatt, a Colorado oil man angry to be forced to do business with Taggart Transcontinental. Dagny promises him that he will get the service he needs. Dagny encounters former lover Francisco d'Anconia, who presents a faÃ§ade of a playboy grown bored with the pursuit of money. He reveals that a series of copper mines he built are worthless, costing his investors (including the Taggart railroad) millions.
Rearden lives in a magnificent home with a wife and a brother who are happy to live off his effort, though they overtly disrespect it. Rearden's anniversary gift to his wife Lillian is a bracelet made from the first batch of Rearden Metal, but she considers it a garish symbol of Hank's egotism. At a dinner party, Dagny dares Lillian to exchange it for Dagny's diamond necklace, which she does.
As Dagny and Rearden rebuild the Rio Norte line, talented people quit their jobs and refuse all inducements to stay. Meanwhile, Dr. Robert Stadler of the State Science Institute puts out a report implying that Rearden Metal is dangerous. Taggart Transcontinental stock plummets because of its use of Rearden Metal, and Dagny leaves Taggart Transcontinental temporarily and forms her own company to finish the Rio Norte line. She renames it the John Galt Line, in defiance of the phrase "Who is John Galt?"âwhich has come to stand for any question to which it is pointless to seek an answer.
A new law forces Rearden to sell most of his businesses, but he retains Rearden Steel for the sake of his metal and to finish the John Galt Line. Despite strong government and union opposition to Rearden Metal, Dagny and Rearden complete the line ahead of schedule and successfully test it on a record-setting run to Wyatt's oil fields in Colorado. At the home of Wyatt, now a close friend, Dagny and Rearden celebrate the success of the line. As Dagny and Rearden continue their celebration into the night by fulfilling their growing sexual attraction, the shadowy figure responsible for the disappearances of prominent people visits Wyatt with an offer for a better society based on personal achievement.
The next morning, Dagny and Rearden begin investigating an abandoned prototype of an advanced motor that could revolutionize the world. They realize the genius of the motor's creator and try to track him down. Dagny finds Dr. Hugh Akston, working as a cook at a diner, but he is not willing to reveal the identity of the inventor; Akston knows whom Dagny is seeking and says she will never find him, though he may find her.
Another new law limits rail freight and levies a special tax on Colorado. It is the final straw for Ellis Wyatt. When Dagny hears that Wyatt's oil fields are on fire, she rushes to his home but finds a handwritten sign that reads, "I am leaving it as I found it. Take over. It's yours."
Wyatt declares in an answering machine message that he is "on strike".

Question: Who replaces the railroad track with Rearden metal?
Answer: Dagny Taggart