Some of the first pictures of the US Army are of Union soldiers during the Civil War. Here's a photo of soldiers camping along the west bank of the Rappahonnock River at Fredericksburg during the Battle of Chancellorsville.
One of the most famous Army units was Teddy Roosevelt's "Rough Riders." They are pictured here after the Battle of San Juan in 1898.
The army began acquiring fixed-wing aircraft in 1910. This photo shows Army planes flying over Manhattan in 1939.
WWI marked the beginning of trench warfare and poison gas. Many of the muddy trenches throughout Europe were plauged with rat and lice infestations and were breeding grounds for disease. Here are American soldiers standing in a trench in 1915.
This 1918 picture shows American soldiers in France wearing gas masks.
On November 11, 1918 the Armistice of Compiègne was signed between the Allies and Germany effectively ending the First World War. Here soldiers are celebrating the end of the war.
The US Army played a pivotal role in World War II, making up the bulk of the American forces during the D-Day invasion on June 6, 1944.
During World War II, the 442nd Regimental Combat Team rose to prominence. It was comprised almost entirely of American soldiers of Japanese descent who volunteered to fight. They are the most decorated force in the history of the US Army.
The Army also fought alongside the Marines in the Pacific against the Japanese. Here, infantrymen advance in the cover of an M4 Sherman tank on the Solomon Islands.
President Truman desegregated the Army in 1948. The Korean War was the first major conflict to have integrated units.
The Army operates a few fixed-wing aircraft, but numerous types of rotary-wing aircraft. Here, US Army helicopters drop off American soldiers during an offensive against the Viet Cong.
Here, a first sergeant guides a medevac helicopter through the jungles of Vietnam.
The Army featured prominently in Operation Desert Storm, the US-led mission to liberate Kuwait from Iraq. Soldiers in the Army's 7th Corps huddle with protective gear fearing a chemical weapons strike by Saddam Hussein after the US started bombing Iraq.
US Army self-propelled 155mm Howitzers assigned to the 7th Corps head towards the Kuwaiti border to force out Iraqi forces.
The Army has also functioned as a police force in war-torn areas. Two soldiers here provide security during a foot patrol in Ramadi, Iraq.
Members of the Army National Guard help serve in peacekeeping missions around the world, as well as aiding U.S. citizens caught up in natural disasters. A member of the Louisiana Army National Guard helps evacuate a child from flooding caused by Hurricane Isaac in 2012.
A Sikorsky UH-60 Black Hawk helicopter drops off a soldier. Black Hawks have been in service since 1979 and cost around $21.3 million.
Soldiers practice repelling out of a Black Hawk helicopter at Fort Hood Air Assault School.
The Army also includes airborne divisions. Paratrooper Staff Sgt. Travis Surber parachutes out of a C-130 Hercules.
The US Army even has its own parachute team.
Of course, the Army also has its own special operations team, the Army Rangers, who trace their lineage back to the Colonial period in the US.
The Army also routinely deploys overseas to help train friendly nations. Here, Soldiers of Charlie Company conduct Fire Phobia Training during a Kosovo Force Mission Rehearsal Exercise at the Joint Multinational Readiness Center in Hohenfels, Germany.
You've seen the history of the US Army ...
