Read about this recently....
Have you guys (esp. guys in US) observed the US $1 currency ? There are some amazing symbolisms on the wings (of the Eagle...).
The Yankees seem to be fixated on the number 13 for various reasons.
United States and Triskaidekaphilia
13 original colonies,
13 signers of the Declaration of Independence,
13 stripes on our flag,
13 steps on the Pyramid,
13 letters in the Latin above,
13 letters in "E Pluribus Unum",
13 stars above the Eagle,
13 bars on that shield,
13 leaves on the olive branch,
13 fruits, and if you look closely, 13 arrows.
And, for minorities: the 13th Amendment.
Find details of the symbolism used here