To calculate the circumference of a circle, you can use the formula:
\[ \text{Circumference} = \pi \times \text{diameter} \]
Given that the diameter is 4.5 miles and using an estimate of \(\pi \approx 3.14\):
\[ \text{Circumference} = 3.14 \times 4.5 \]
Now, perform the multiplication:
\[ 3.14 \times 4.5 = 14.13 \]
Thus, the estimated circumference of the circle is 14.13 miles.