He was born in Mitchell, Indiana and earned a B.S. in mechanical engineering from Purdue University in 1950. He was married with two children.
He was chosen with the first group of astronauts in 1959. He was pilot for Mecury-Redstone 4 ("Liberty Bell 7"), the second american (suborbital) spaceflight, and command pilot for the first manned Gemini mission (Gemini 3), as well as backup command pilot for Gemini 6, and had been selected as commander of the first Apollo program flight at the time of his death.
There was a desire in NASA management for one of the original Mercury Seven to be the first man to walk upon the moon. Had Gus lived, he would very likely have been that man.
Grissom died along with fellow astronauts Edward White and Roger Chaffee in the Apollo 1 fire at Cape Kennedy.