My first ever triathlon was the 2005 Glenview Park Center Sprint Triathlon.  I finished in 1:12:35 and was 117th out of 286 which was the 40th percentile.

ID#  PLACE CLASS     FINISHER                       TIME
184  117   10 – M20  John Crane, 25, Evanston, IL   72:35.0

Official Results are here