Thousands of runners come to the Boston Marathon to run in its famous event each year. The Boston Marathon course is 46,145 yards long. What is the best estimate of the length of the course in feet?

One yard is equivalent to 3 feet.

Therefore, 46,145 yards x 3 feet = 138,435 feet

So, the best estimate of the length of the Boston Marathon course in feet is 138,435 feet.