The Hughes H1, the last privately built air speed record holder, 1935. All since have been military

It set a world airspeed record and a transcontinental speed record across the United States.

The H-1 Racer was the last aircraft built by a private individual to set the world speed record; every aircraft to hold the honor since has been a military design. The H-1 first flew in 1935 and promptly broke the world landplane speed record with Hughes at the controls, clocking 352 mph (566 km/h) averaged over four timed passes.

Found on http://dailytimewaster.blogspot.com/2013/07/get-load-of-this.html