To find the length of the edge of the square base, we can use the Pythagorean Theorem.
Let the side of the square base be x.
We know that the height of the pyramid is 321 ft and the slant height is 436.5 ft.
Using the Pythagorean Theorem, we have:
x^2 + x^2 = 321^2
2x^2 = 103041
x^2 = 51520.5
x = sqrt(51520.5)
x β 226.9 ft
Therefore, the length of the edge of the square base is approximately 226.9 feet.