Changed history? You cannot "change" history, only make it. Of those, some of my favorites are:
The Wright Brothers, powered flight
Glenn Curtiss, inventor
Dr. Alexander Graham Bell, inventor of the telephone and aileron technology.
Thomas Edison, inventor, missed getting his telephone patented by merely minutes.
Major Gregory Boyington, USMC, the only man to form a USMC squadron without congressional approval.
Pres. Dwight D. Eisenhower (Republican) ordered the desegregation of both the military and public schools. The Democrats fought him on it and forced him to call out the National Guard to enforce it.