When President Trump went to Walter Reed Military Medical Center on Friday evening -- "out of an abundance of caution" after testing positive for COVID-19 -- he entered a facility that has a long history of serving U.S. presidents as well as men and women who've served in the armed forces.

The White House said Trump was expected to stay "a few days" at the hospital, which has a presidential suite that will allow him to continue his official duties.

Known as the "Presidents' Hospital," every president since Franklin D. Roosevelt has been treated there, according to Navy Medicine.

The present iteration of the hospital formed in September 2011 when the National Naval Medical Center and the Walter Reed Army Medical Center combined to become the Walter Reed National Military Medical Center.

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But the history of the hospital goes back much further than that. Walter Reed General Hospital first opened in 1909. It is named after Maj. Walter Reed, a U.S. Army physician best known for discovering that yellow fever is transmitted by mosquitoes.

Meanwhile, the National Naval Medical Center was spearheaded by FDR, who served as assistant secretary of the Navy from 1913-1920, and was able to bring his vision for the hospital to fruition as president in 1939.

"He drew a sketch of the building on White House stationery, reminiscent of the State Capitol Building in Lincoln, Nebraska, which he admired," the Walter Reed Society writes. "This sketch became the template for the design of the new Naval Medical Center."

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The 2011 merging of the two medical centers into the Walter Reed Military Medical Center created the world's largest joint military medical center with 2.4 million square feet of clinical space and roughly 7,100 staff members.

Many of the presidential visits over the years have been for routine check-ups to ensure the country's commander-in-chief is in good health. President Trump last went for his annual physical in November 2019.

But other major operations have also taken place there. President Lyndon B. Johnson had his gallbladder removed at the hospital in October 1965. Ronald Reagan had colon and skin cancer surgeries there.

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When John F. Kennedy was assassinated, the Secret Service demanded that he be taken to the President's Hospital.

"On November 22, 1963, America’s 35th President John F. Kennedy was assassinated," the Walter Reed Society writes. "Doctors and coroners at Parkland Memorial Hospital in Dallas intended to do the autopsy, but the Secret Service demanded that the President’s body be taken to “The President’s Hospital” for the autopsy, which was performed on the evening of November, 22, 1963."

Aside from Presidents, the hospital has also treated countless members of Congress and Supreme Court Justices.

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The Associated Press contributed to this report.