Happy Birthday, America!

Across

Material of elephant's tusks (5)
Free and equal representation of people (9)
See 1 Down
Stitch (3)
10 Most desirable or favorable (7)
12 Student (5)
14 Big and strong in physique (5)
16 Large Australian flightless bird (3)
17 Abbreviation of National Basketball Association (3)
18 Walk leisurely (5)
19 A useful or valuable quality (5)
20 National Emblem (5)
22 Military trainee (5)
23 A large African antelope (3)
24 Prompt or reminder (3)
25 A cut-glass object (5)
26 Time when somebody is young (5)
27 The Star Spangled Banner is the National ______ (6)
29 To cheat somebody, especially by overcharging (informal) (3)
31 Expressing disapproval (3)
32 Bright exploding objects (9)
33 Long-necked water birds (5)

Down

1/8 Fourth of July (12,3)
Capital of Washington (7)
An affirmative (3)
Water droplets (3)
The sound made by a cow (3)
Saying spiteful things about somebody, especially in a subtle way (5)
Without purpose or direction (7)
11 Memorial in South Dakota, featuring the heads of four U.S. presidents (5,8)
13 Go away from a place (5)
14 A portable charcoal-burning brazier (7)
15 Right to act or speak freely (7)
19 Tensely nervous or apprehensive (5)
21 Grass is always ______ on the other side (7)
23 To complain or mutter in a discontented way (7)
25 Used to express disbelief, impatience, or contempt (5)
28 Make imperfect (3)
29 Fossil fuel (3)
30 Dog with a wrinkled face (3)