José Rios Gallardo (b. 1932) was a Cuban-born American minor league baseball player. His career appears to have lasted only one season, in 1954, when he played with the Artesia NuMexers. He is probably best remembered for pitching what became Joe Bauman's record-breaking 70th homerun.
Harry Turtledove spells Gallardo's name as "Galardo" in the story. Given how little information is available about Gallardo, it is unclear whether this is an inconsistency, or if he did change the spelling of his name at some point.