Who broke the sound barrier ?

Charles Elwood “Chuck” Yeager (born February 13, 1923) is a retired Brigadier General in the United States Air Force and a noted test pilot. In 1947, he became the first pilot to travel faster than sound in level flight and ascent.
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US efforts started soon after Britain had disclosed all its research and designs to the US government, on the promise that US information would be shared the other way. The US failed to disclose any information in return, stating the Pentagon had deemed the project Top Secret. They took the technological information provided by the British and began work on the Bell XS-1.

The final version of the Bell XS-1 has many design similarities to the original Miles version. Also featuring the all-moving tail, the XS-1, later known as the X-1. It was in the X-1 that Chuck Yeager was the first person to break the sound barrier in level flight on October 14, 1947, flying at an altitude of 45,000 ft (13.7 km).
(source: wikipedia)