Final answer:
The sun passes directly overhead at Acadia National Park in Maine twice a year, during the summer and winter solstices.
Step-by-step explanation:
The sun will pass directly overhead at Acadia National Park in Maine (44 degrees 21' N, 68 degrees 13' W) twice a year. This occurs during the summer and winter solstices, which usually fall around June 21st and December 21st respectively. During these times, the sun reaches its highest and lowest points in the sky, resulting in it being directly overhead at certain latitudes.