It is a fact that were about 50,000 casualties at Gettysburg. But as you correctly noted, casualties doesnt mean deaths.
To illustrate that with an example, two of the casualties. were Union Colonel Chamberlain and Confederate General Kemper. Some years later Chamberlain became Governor of Maine, Kemper became Governor of Virginia.
Chamberlain's regiment defended Little Round Top from attacking Confederate troops commanded by William Oates - a battle that might well have decided the outcome of the war. As you noted, Chamberlain was subsequently elected governor of Maine; Oates went on to be elected governor of Alabama. IIRC, a line connecting the places where the two men were born passes through Pennsylvania, with Gettysburg located at the approximate midpoint...
;^)