What was the primary occupation of James Marshall at the time he discovered gold?

James Marshall was primarily engaged as a sawmill builder at the time he discovered gold in 1848. He was working on the construction of a sawmill for John Sutter, which was located on the American River. Marshall's discovery of gold occurred while he was inspecting the waterwheel for the sawmill. This discovery led to the California Gold Rush, a pivotal event in California's history that attracted thousands of fortune seekers to the region.

The other occupations listed do not represent his primary role during this time. While many individuals became miners during the Gold Rush, Marshall was not one of them at the time of his discovery; he was focused on the sawmill project. Being a farmer or a photographer are also not accurate representations of his situation, as he was not engaged in those activities when he stumbled upon the gold that would change California's destiny.