Lifelong rivals collaborate on a 19th-century moon rocket.

In 1868 America, munitions mogul and inventor Victor Barbicane calls a meeting of the International Armaments Club at his sprawling mansion, Victory, to inform them of his development of an extremely powerful explosive, "Power X." Barbicane explains that a rocket carrying Power X could destroy an entire city and, because of its dangerous properties, proposes building a great rocket to travel to the moon where he will test the abilities of Power X. Numerous wealthy businessmen in the club, including Josef Cartier, author Jules Verne, banker Morgana and scientist Aldo Von Metz, agree to support Barbicane's fantastic project. Word rapidly spreads of Barbicane's construction of a "super-rocket," horrifying prominent metallurgist Stuyvesant Nicholl, a serious, religious man, who challenges Barbicane to a duel. When Barbicane refuses, Nicholl goes to Washington, D.C. where he reports to Congress that he has forged the hardest substance known to man and, insisting that Barbicane is lying about the potential of Power X, demands that Barbicane test it against his invention. Barbicane agrees and a test is soon arranged. Using only a few drops of Power X in a small bullet-shaped projectile, Barbicane not only completely annihilates Nicholl's metal shield, but demolishes the mountain behind it. Plans for building the rocket proceed, providing employment and enthusiasm in the region, until Barbicane is summoned by President Ulysses S. Grant to a secret meeting. Grant informs the inventor that many nations believe that Power X gives America an unfair military advantage over them and twenty-two nations have stated that if Barbicane's experiment is completed, they will consider it an act of war. Barbicane declares that as a scientist he has the right to test his invention, but Grant insists that internationally the trial is seen as a ruse to cover America's play for global dominance. Barbicane reluctantly agrees to call off his experiment and accedes to the president's request not to reveal the reasons for the decision. After Barbicane's announcement of the cancellation of the Power X rocket, disgruntled investors and an expectant public attack him in the press. Several businessmen led by Morgana demand to purchase Power X from Barbicane, but he rejects their offer. Undaunted, Barbicane continues his scientific inquiries and upon examining the small remains of Nicholl's shield from the test, learns that the fused material is indeed harder than any other substance. Barbicane realizes that he can use the substance to create a rocket that, fueled by Power X, will be safe enough to transport men into outer space. Barbicane meets with Nicholl and his daughter Virginia to request his help in building the rocket and, convinced that reaching the moon will be a great human achievement, Nicholl agrees. When the rocket is completed, Virginia christens it "Columbia," and unknown to her father, Barbicane and his young assistant Ben Sharpe, she then sneaks onboard and hides in one of the pressurized space suits. Unaware of the stowaway, the men climb into special acceleration tubes and the rocket is successfully launched. In the air, Barbicane toasts to their success, but Nicholl admits he believes that the flight flaunts God's natural laws. When the ship's enormous gyroscope goes awry, Nicholl confesses that he sabotaged the ship's rockets, determined to discredit Power X. When a gas leak prompts Ben to go below to retrieve the space suits, he is startled to find Virginia, who is dismayed to learn of her father's sabotage. Realizing the ship could explode at any moment, Barbicane attempts to repair Nicholl's damage, but is caught in an electronic burst in which Nicholl intentionally allows him to be shocked. Virginia is horrified by her father's behavior, but he insists he is doing God's will. Shortly after Barbicane recovers, the rocket flies into a meteor shower and Nicholl grudgingly admires the abilities of the Columbia. On Earth at an observatory tracking the rocket, Von Metz spots the great sparks given off by Columbia's flight through the meteors and believes the ship has been destroyed. Newspaper publisher Bancroft tells Barbicane's supporters that he suspects the entire flight is a hoax and that Barbicane has absconded with the contributors' funds and gone into hiding nearby. On board the rocket, Barbicane informs Nicholl of his intention to sell every nation on Earth Power X and his confidence that because mankind would rather live than destroy itself, the substance would eventually be used for the greater good. Stunned by the notion, Nicholl is contrite about trying to destroy Power X, but Barbicane tells him that Power X is found in nature and will be discovered again in time. Barbicane soon realizes the ship will be unable to escape the moon's gravitational pull unless they can fire the damaged rockets to break free. Nicholl comes to Barbicane's aid when he again attempts to make repairs. Barbicane then suggests they try firing the rockets, sending the return module toward Earth while the rest of the ship might be pushed toward the moon. Ben insists on helping, but Nicholl knocks him out and places him with the distraught Virginia in the module. Barbicane fires the rockets successfully, sending Ben and Virginia back to Earth while he and Nicholl fall to the moon. Noting the rocket's explosion from the observatory, Von Metz concludes the ship reached the moon only to blow up. As Ben guides the module to Earth, Virginia worries about her father until they see a small burst of light from the moon's surface. Virginia is delighted that Earth has seen the signal, but Ben points out that it came from the moon side facing away from Earth and was meant for them as a sign that Barbicane and Nicholl landed safely. Ben assures Virginia that other men will someday fly to the moon again and that Barbicane and Nicholl will never be forgotten.