In a rematch of last year's championship game, Underwood dominated the Wildcats again with a strong defensive effort. Maquoketa Valley made just three field goals in the second half and shot just 17.5 percent from the field.
Boyd led all scorers with 19 while Meghan Brue tallied nine points with a game-high 12 rebounds. The Hawks outrebounds Maquoketa Valley, 40-30.
Ashley Nordmann led Maquoketa Valley with seven points and seven rebounds.
Underwood advances to the Class 2A championship game at 8:30 Friday. Maquoketa Valley ends its season at 24-3.
Underwood (26-1) 15 14 8 7 -- 44
Maquoketa Valley (24-3) 11 4 8 6 -- 29