Originally Posted by IslandRed
Slight correction -- it's 1 1/2 miles on dirt (i.e. his Belmont Stakes performance), and that 2:24 is still the world record for that distance on dirt. Considering the Belmont Stakes is just about the only 1 1/2 mile dirt race left in the world -- pretty much everything else at that distance is on turf -- it may stand forever.
Actually I was wrong, but not for the reason you think. Secretariat ran 2:24 4/5 on the grass in the Man O' War setting the 1 1/2 grass record that stood at Belmont for many years, and according to Wikepedia is still the track record.
However I see that in 2001 a horse called Fantastic Light ran the distance on the grass in 2:24.36. So after 40 years Secretariat only holds 2 track records at Belmont, not 3.