Liberty (freedom of speech, freedom of religion, freedom of press, etc.)
Equality (everyone has equal opportunity and is treated the same)
The common good (benefits or interest everyone)
the birth of the United States as an independent nation
military veterans who served our country
American labor movements and the workers/contributors of labor to the development and achievement of the U.S.
13 stripes which represent the original 13 colonies and 50 starts to represent 50 states of the Union