To calculate the area of a square, you use the formula:
\[ \text{Area} = \text{side} \times \text{side} \]
In your case, the side of the square is 13 feet.
\[ \text{Area} = 13 , \text{feet} \times 13 , \text{feet} = 169 , \text{square feet} \]
Therefore, the correct answer is:
169 ft.² or 169 ft. squared.