user: Question: What is the highest River Mile that has a pool length of 42.2 miles or a lock/lift drop of 21 feet?
Columns: ['Locks & Dam', 'Location [L ]', 'River Mile', 'Lock Side', 'Lock Lift/Drop (in feet)', 'Pool Length (miles)']
Types: ['text', 'text', 'real', 'text', 'text', 'text']
Sample row: ['Emsworth Locks and Dam', 'Pittsburgh, Pennsylvania', 6.2, 'RDB', '18', '6.2+']
SQL:

assistant: SELECT MAX("River Mile") FROM "Table" WHERE "Pool Length (miles)" = '42.2' AND "Lock Lift/Drop (in feet)" = '21';