Final answer:
The Hoover Dam was decided to be built in its known location in the Black Canyon to control floods and droughts, generate hydroelectric power, and irrigate land in the American Southwest.
Step-by-step explanation:
The Hoover Dam was decided to be built in its known location due to several reasons. First, as western expansion led to development in the American Southwest, settlers realized the need to control floods and droughts for agriculture. In 1922, the U.S. Bureau of Reclamation chose the Black Canyon as a good location for a dam to divert the Colorado River. The dam was authorized by Congress in 1928, and construction began in 1931.
The Hoover Dam served the dual purpose of generating hydroelectric power and irrigating two million acres of land from the resulting reservoir, Lake Mead. Additionally, the dam provided a source of employment during the Great Depression. It was the largest concrete structure in the world at the time of its construction, standing 726 feet tall.