The length of one side of the region containing the small squares is 64 inches.
Let x be the length of one side of the region containing the small squares.
The area of the small squares is 64 * 1 = 64 square inches.
The area of the border is (x + 2)^2 - x^2 = 4x + 4 square inches.
Since the area of the small squares and the border is equal to the area of the chessboard, we have:
64 + 4x + 4 = 324
68 + 4x = 324
4x = 256
x = 64
Therefore, the length of one side of the region containing the small squares is 64 inches.