user: Question: What was the earliest year for the USISL Pro League?
Columns: ['Year', 'League', 'Reg. Season', 'Playoffs', 'Open Cup']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1994.0, 'USISL', '5th, Atlantic', 'Divisional Semifinals', 'Did not enter']
SQL:

assistant: SELECT MIN("Year") FROM "Table" WHERE "League" = 'USISL Pro League';