Romero won purses totaling more than $75 million in his 26-year career.
Santos rode Funny Cide to wins in the 2003 Kentucky Derby and Preakness Stakes and has piled up more than $155 million in purses in his career.
Solis, winner of the 1986 Preakness Stakes, has piled up more than $206 million in winnings.
Trainers nominated this year are Gary Jones, John Veitch and Robert Wheeler.
Male horses on the ballot are 1992 Santa Anita Handicap winner Best Pal, 1986 champion male turf horse Manila and 1997 Kentucky Derby and Preakness winner Silver Charm. Female horses being considered are 1995 Breeders' Cup Distaff champ Inside Information, 1985 champion 3-year-old filly Moms Command, two-time Eclipse Award winner Silverbulletday and Sky Beauty who was the 1994 champion older female.
The 2007 National Museum of Racing's Hall of Fame class will be announced May 29. Formal induction ceremonies are set for Aug. 6 in Saratoga Springs, N.Y.