A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil works.

USACE has 37,000 civilian and military personnel,[2] making it one of the world's largest public engineering, design, and construction management agencies.

For the military construction mission, the chief of engineers is directed and supervised by the Assistant Secretary of the Army for installations, environment, and energy, whom the President appoints and the Senate confirms.

Army civil works include three U.S. Congress-authorized business lines: navigation, flood and storm damage protection, and aquatic ecosystem restoration.

[4] The corps's mission is to "deliver vital public and military engineering services; partnering in peace and war to strengthen our nation's security, energize the economy and reduce risks from disasters.

"[5] Its most visible civil works missions include: The history of United States Army Corps of Engineers can be traced back to the American Revolution.

The Continental Congress recognized the need for engineers trained in military fortifications and asked the government of King Louis XVI of France for assistance.

Louis Lebègue Duportail, a lieutenant colonel in the French Royal Corps of Engineers, was secretly sent to North America in March 1777 to serve in George Washington's Continental Army.

[9] Separately authorized on 4 July 1838, the Corps of Topographical Engineers consisted only of officers and was used for mapping and the design and construction of federal civil works and other coastal fortifications and navigational routes.

[citation needed] In 1944, specially trained army combat engineers were assigned to blow up underwater obstacles and clear defended ports during the invasion of Normandy.

[18] Working in camouflage, the Pioneers cleared jungle, prepared routes of advance and established bridgeheads for the infantry, as well as demolishing enemy installations.

[18] Five commanding generals (chiefs of staff after the 1903 reorganization) of the United States Army held engineer commissions early in their careers.

USACE has two civilian directors who head up Military and Civil Works programs in concert with their respective DCG for the mission area.

USACE directly supports the military in the battle zone, making expertise available to commanders to help solve or avoid engineering (and other) problems.

In both its Civil Works mission and Military Construction program, the Corps of Engineers is responsible for billions of dollars of the nation's infrastructure.

The Army adopted a sustainability policy in the early 2000s to make military bases, and the force as a whole, more resilient and less dependent on fossil fuels.

Since the US military is one of the world's largest institutional energy consumers, this would have a significant impact on reducing waste, improving efficiency, and ensuring that public resources are used effectively.

[44] The Army has developed and adopted its own triple bottom line framework shifting from the traditional "People Planet, and Profit" to "Mission, Community, and Environment".

[47] Summary of facts and figures as of 2007, provided by the Corps of Engineers:[28][needs update] The regulatory program is authorized to protect the nation's aquatic resources.

USACE personnel evaluate permit applications for essentially all construction activities that occur in the nation's waters, including wetlands.

Section 10 of the Rivers and Harbors Act of 1899 (codified in Chapter 33, Section 403 of the United States Code) gave the Corps authority over navigable waters of the United States, defined as "those waters that are subject to the ebb and flow of the tide and/or are presently being used, or have been used in the past, or may be susceptible for use to transport interstate or foreign commerce."

The Secretary of the Army is authorized under this act to issue permits for the discharge of dredged and fill material in waters of the United States, including adjacent wetlands.

Select nationwide permits require preconstruction notification to the applicable corps district office notifying them of his or her intent, type and amount of impact and fill in waters, and a site map.

[51] A current tradition was established with the "Gold Castles" branch insignia of General of the Army Douglas MacArthur, West Point Class of 1903, who served in the Corps of Engineers early in his career and had received the two pins as a graduation gift of his family.

Some projects are said to have created profound detrimental environmental effects or provided questionable economic benefit such as the Mississippi River–Gulf Outlet in southeast Louisiana.

[55] Faulty design and substandard construction have been cited in the failure of levees in the wake of Hurricane Katrina that caused flooding of 80% of the city of New Orleans.

Local citizen, special interest, and political groups lobby Congress for authorization and appropriations for specific projects in their area.

[59] Senator Russ Feingold and Senator John McCain sponsored an amendment requiring peer review of Corps projects to the Water Resources Development Act of 2006,[60] proclaiming "efforts to reform and add transparency to the way the U.S. Army Corps of Engineers receives funding for and undertakes water projects."

A similar bill, the Water Resources Development Act of 2007, which included the text of the original Corps' peer review measure, was eventually passed by Congress in 2007, overriding Presidential veto.

[62][63] Bunnatine "Bunny" Greenhouse, a formerly high-ranking official in the Corps of Engineers, won a lawsuit against the United States government in July 2011.