CREATE TABLE table_10481 ("Date" TEXT, "Track" TEXT, "Race" TEXT, "Dist." TEXT, "Purse  (  US$  ) " TEXT, "Track Surf." TEXT, "Winning horse" TEXT, "Win jockey" TEXT)

What was the Illinois Derby purse?
SELECT "Purse ( US$ )" FROM table_10481 WHERE "Race" = 'illinois derby'
SELECT "Purse ( US$ )" FROM "table_10481" WHERE "Race" = 'illinois derby'