The Right Stuff

In 1947, the Muroc Army Air Field in California has test pilots fly high-speed aircraft such as the rocket-powered Bell X-1, but they die as a result. After another pilot, Slick Goodlin, demands $150,000 to attempt to break the sound barrier, war hero Captain Chuck Yeager receives the chance to fly the X-1. While on a horseback ride with his wife Glennis, Yeager collides with a tree branch and breaks his ribs, which inhibits him from leaning over and locking the door to the X-1. Worried that he might not fly the mission, Yeager confides in friend and fellow pilot Jack Ridley. Ridley cuts off part of a broomstick and tells Yeager to use it as a lever to help seal the hatch to the X-1, and Yeager becomes the first person to fly at supersonic speed, defeating the "demon in the sky".
Six years later, Muroc, now Edwards Air Force Base, still attracts the best test pilots. Yeager (now a major) and friendly rival Scott Crossfield repeatedly break the other's speed records. They often visit the Happy Bottom Riding Club run by Pancho Barnes, who classifies the pilots at Edwards as either "prime" (such as Yeager and Crossfield) that fly the best equipment or newer "pudknockers" who only dream about it. Gordon "Gordo" Cooper, Virgil "Gus" Grissom and Donald "Deke" Slayton, captains of the United States Air Force, are among the "pudknockers" who hope to also prove that they have "the Right Stuff". The tests are no longer secret, as the military soon recognizes that it needs good publicity for funding, and with "no bucks, no Buck Rogers". Cooper's wife, Trudy, and other wives are afraid of becoming widows, but cannot change their husbands' ambitions and desire for success and fame.
In 1957, the launch of the Russian Sputnik satellite alarms the United States government. Politicians such as Senator Lyndon B. Johnson and military leaders demand that NASA help America defeat the Russians in the new Space Race. The search for the first Americans in space excludes Yeager because he lacks a college degree. Grueling physical and mental tests select the Mercury Seven astronauts, including John Glenn of the United States Marine Corps, Alan Shepard, Walter Schirra and Scott Carpenter of the United States Navy, as well as Cooper, Grissom and Slayton; they immediately become national heroes. Although many early NASA rockets explode during launch, the ambitious astronauts all hope to be the first in space as part of Project Mercury. Although engineers see the men as passengers, the pilots insist that the Mercury spacecraft have a window, a hatch with explosive bolts, and pitch-yaw-roll controls. However, Russia beats them on April 12, 1961 with the launch of Vostok 1 carrying Yuri Gagarin into space. The seven astronauts immediately decide to start the Mercury program.
Shepard is the first American to reach space on the 15-minute sub-orbital flight of Mercury-Redstone 3 on May 5. After Grissom's similar flight of Mercury-Redstone 4 on July 21, the capsule's hatch blows open and quickly fills with water. Grissom escapes, but the spacecraft, overweight with seawater, sinks. Many criticize Grissom for possibly panicking and opening the hatch prematurely. Glenn becomes the first American to orbit the Earth on Mercury-Atlas 6 on February 20, 1962, surviving a possibly loose heat shield, and receives a ticker-tape parade. He, his colleagues, and their families become celebrities, including a gigantic celebration in the Sam Houston Coliseum to announce the opening of the Manned Space Center in Houston, despite Glenn's wife Annie's fear of public speaking due to a stutter.
Although test pilots at Edwards mock the Mercury program for sending "spam in a can" into space, they recognize that they are no longer the fastest men on Earth, and Yeager states that "it takes a special kind of man to volunteer for a suicide mission, especially when it's on national TV." While testing the new Lockheed NF-104A, Yeager attempts to set a new altitude record at the edge of space but is nearly killed in a high-speed ejection when his engine fails. Though seriously burned, after reaching the ground Yeager gathers up his parachute and walks to the ambulance, proving that he still has the Right Stuff.
On May 15, 1963, Cooper has a successful launch on Mercury-Atlas 9, ending the Mercury program. As the last American to fly into space alone, he "went higher, farther, and faster than any other American ... for a brief moment, Gordo Cooper became the greatest pilot anyone had ever seen."

Question: Who was the last American to fly into space alone?
Answer: Cooper