Much of the nation's infrastructure was built on the proverbial back of the US Army Corps of Engineers (USACE). In the 19th and 20th centuries, it built coastal fortifications, improved harbors, eliminated navigation hazards on key rivers, surveyed roads and canals, protected natural resources, constructed buildings and monuments, and explored and mapped much of the western frontier. Today, the USACE is the world's largest public engineering, design, and construction management agency and is involved in research and development, military contingencies, humanitarian assistance, environmental protection, and water resource development. The USACE employs some 37,000 civilians and about 550 soldiers.
The USACE owns and operates about 700 dams that are used for hydroelectric power generation, flood control, and water supply.
The agency also responds to natural disasters and other emergencies as the nation's primary engineering agency, supporting the Federal Emergency Management Agency.
It additionally does reimbursable work for other organizations, such as cleaning up toxic and hazardous waste for the Environmental Protection Agency.