The correct answer to this open question is the following.
The three individuals that I picked, who shaped Nevada history between 1900 and 1945 were Patrick McCarran and James G. Scrugham.
What makes them significant to Nevada is the following.
In the case of James G. Scrugham, he was the governor of the state of Nevada from 1923 to 1927 and supported the construction of the Colorado River dam that would benefit the area of Las Vegas and its surroundings. He improved the highway system of the state and also supported the creation of a park administration.
Patrick McCarran was a prominent politician and Senator that promoted the idea of constructing a major airport in Las Vegas. He also contributed to bringing different US military bases to the state.
