user: Question: What year did Negro American League join?
Columns: ['Team', 'Sport', 'League', 'Established', 'Began in St. Louis', 'Venue', 'Championships in St. Louis', 'Left St. Louis']
Types: ['text', 'text', 'text', 'real', 'real', 'text', 'text', 'real']
Sample row: ['St. Louis Stampede', 'Arena Football', 'Arena Football League', 1987.0, 1994.0, 'Scottrade Center', '0', 1995.0]
SQL:

assistant: SELECT "Began in St. Louis" FROM "Table" WHERE "League" = 'Negro American League';