The history of engineering is a history of breaking barriers and in aviation we all know one barrier that seems easy on today’s planes to break but was a huge trouble in late 40s, and yes, it’s the sound barrier.
Back in the World War II, the necessity of having faster and better planes than the enemy lead to a great jump in aviation technology: the mad engineering of the P-47, the pure aerodynamics of the P-51 or the invention of the jet planes are great examples of this. But a problem appeared: when getting faster they were getting closer to the speed of sound, and certainly nobody knew if it was possible to surpass.
After the war, the USA had the technology, the money and most of the German engineers, such as Von Braun, thanks to the Operation Paperclip so the US Air Force (The US Army Air Forces back then) started a project of experimentation in new technologies and planes, leading to the X-plane program where the aircraft remain on a strict secret during their development. The first of them was the Bell X-1 (How not?) and its main purpose was to break the sound barrier.
Regarding the plane, it was propelled by a rocket engine and its design was focused on aerodynamics to reduce the air friction at the minimum possible, so it has its characteristic fuselage that seems more like a round dart. The first flight occurred on December 9th of 1946 and the pilot was Chalmers Goodlin. Notice that these planes were launched from a B29 Super Fortress bomber.
However, during the flights, trouble started when reaching Mach 1, the shock waves started to shake the plane, making it dangerously uncontrollable when this wave reached the control tabs, forcing them to abort the mission constantly.
Wasn’t until Chuck Yeager that the plane completely crossed the shock wave, Chuck noticed that once the plane gets enough speed it fully goes through the shockwave, so it appeared behind the aircraft and the shaking disappeared. This flight reached 1100 km/h which translates to a Mach 1.06 at an altitude of 12800 m. The Bell X1 flown by Chuck was named Glamourous Glennis.
Yet Chuck Yeager is officially recognized as the first person that went through the sound barrier some other pilots claim this title, such as F86’s pilot George Welch or the German Hans Guido in a Me262 during the WW2.
Although, we can doubt in which was the first pilot in crossing the sound barrier what we can’t doubt is that when Chuck Yeager first saw a jet, he shot it down.
Straight rear view of the Bell X-1 “Glamorous Glennis” (A19510007000) on the floor with black background 
Detail view of the exterior fuselage of the Bell X-1 “Glamorous Glennis” (A19510007000) 
Close-up right side view of the nose of the Bell X-1 “Glamorous Glennis” (A19510007000), hatch removed, silhouetted on black background 
Straight front head-on view of the Bell X-1 “Glamorous Glennis” (A19510007000) on the floor 
Straight front head-on view of the Bell X-1 “Glamorous Glennis” (A19510007000) 
Detail view of the exterior fuselage of the Bell X-1 “Glamorous Glennis” (A19510007000)