The first American to win a Nobel Prize was ______ for measuring the speed of light.

The first American to win a Nobel Prize was Albert Michelson, who received the award in 1907 for his precision measurements of the speed of light. Michelson's groundbreaking work involved developing advanced measuring instruments that allowed for highly accurate determination of this fundamental constant. His experiments not only contributed to the field of physics but also helped solidify the scientific method of precision measurement, which has been essential in furthering our understanding of light and optics.

In contrast, while figures like Albert Einstein, Grimaldi, and Thomas Young contributed significantly to physics, they did not achieve the distinction of being the first American Nobel laureate. Einstein is known for his theory of relativity, Grimaldi for his work on the diffraction of light, and Young for the wave theory of light; none of them focused on the specific measurements for which Michelson was recognized. Thus, Michelson stands out as the first American Nobel Prize winner specifically for his accomplishments related to measuring the speed of light.