In his seventeen seasons in the big leagues — all wearing the Birds on the Bat — Bob Gibson was one of the best. Per fWAR he is the sixteenth most valuable pitcher of all time. He ended his career in 1975 with 82.3 total fWAR, a 2.91 ERA, a 2.89 FIP. and a final record of 251-174. He was really dang good.
His best year by ERA was historic. In 1968 Bob Gibson set the record for the lowest ERA in a single season at 1.12. He had a pretty good year. According to my Cardinals calendar, though, his most dominant part of that year was an eleven-start stretch from June 6 through July 30.