XLISP (and therefore XLISP-STAT) had rational numbers[1] and came out in 1988, R2RS[2] introduced rational numbers in 1985. The Lisp Machines Lisps had rational numbers. There were a lot of people who had rational numbers in the 1980s and the early 1990s.
[1] http://people.sju.edu/~jhodgson/ppl/lisp/lispman.txt [2] https://dspace.mit.edu/handle/1721.1/5600