Barrosa Boy must have gone close.
Umrum was the horse I was referring to:
Stakes or Principal Race Wins
Year Race Name Status Distance
1999 VATC Toorak Handicap G1 1600m
2000 VATC Toorak Handicap G1 1600m
1998 VRC Craiglee Stakes G2 1600m
2000 WATC Lee Steere Stakes G2 1400m
1997 SAJC Sires' Produce Stakes G3 1600m
1996 SAJC Fulham Park Plate L 900m
1997 SAJC Sunsmart Stakes L 1500m
1997 VATC JD Macdonald Stakes L 1400m
1997 VRC Concept Sports Stakes L 1417m
2003 TRC Tattersall's Thomas Lyons Stakes L 1400m
2003 TTC Tatt's George Adams Plate L 1600m
Bomber Bill won stakes races in 4 states and was placed in Qld
Stakes or Principal Race Wins
Year Race Name Status Distance
1998 WATC Karrakatta Plate G1 1200m
2001 MVRC Australia Stakes G1 1200m
2003 SAJC Goodwood Handicap G1 1200m
2002 AJC Challenge Stakes G2 1000m
2004 MVRC Schweppervescence Stakes G2 1000m
1998 WATC Sires' Produce Stakes G3 1400m
2000 VRC Gilgai Stakes G3 1200m
2002 AJC Liverpool City Cup G3 1200m
2003 SAJC RN Irwin Stakes G3 1100m
2003 VRC Gilgai Stakes G3 1200m
2005 SAJC Malyasia Airlines Stakes G3 1100m
2006 MRC Rubiton Stakes G3 1000m
1998 VRC Hilton On The Park Sprint L 1100m
1998 WATC Perth Stakes L 1100m
1999 VRC Kensington Stakes L 1100m
2000 VRC Hilton On The Park Sprint L 1100m
2005 MRC Kevin Heffernan Stakes L 1300m
There may well be a horse that has won in every state. Just that there are few publicly available older records of non-stakes races. Very difficult one to track down.