SELECT MAX(river_mile) FROM table_name_71 WHERE pool_length__miles_ = "42.2" AND lock_lift_drop__in_feet_ = "21"
Berapa mil sungai tertinggi yang memiliki panjang kolam 42,2 mil atau tetes kunci/angkat 21 kaki?
CREATE TABLE table_name_71 (river_mile INTEGER, pool_length__miles_ VARCHAR, lock_lift_drop__in_feet_ VARCHAR)