CREATE TABLE table_74504 ("Year" FLOAT, "League" CLOB, "Reg. Season" CLOB, "Playoffs" CLOB, "Open Cup" CLOB)

What was the earliest year for the USISL Pro League?
SELECT MIN("Year") FROM table_74504 WHERE "League" = 'usisl pro league'
SELECT MIN("Year") FROM "table_74504" WHERE "League" = 'usisl pro league'