Ahead of a Facebook-advertised "storming" of Area 51, Jesse Watters considered whether President Trump has been told about what goes on at the secretive military installation.

If Trump is privy to top-secret information about the base, which has long been a point of discussion for conspiracy theorists who believe the facility holds government secrets about aliens and UFOs, it is surprising he hasn't told the public, Watters said on "The Five."

"I am surprised Trump has not slipped up about Area 51 yet," he joked.

"The man cannot keep a secret. I don't even think they told him about Area 51."

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The "Watters' World" host added Trump is often unusually open at campaign events -- to a greater extent than past presidents.

"He'll just let it go at a rally," he said. "But if he has kept that secret, I am very proud."

On Facebook, a page advertising the purported event went viral over the past week, as more than 1 million users responded they would go to the top-secret military installation on Sept. 20 at 3 a.m., with the creator writing "they can't stop all of us."

While it isn’t exactly known what the base is currently used for, Air Force spokeswoman Laura McAndrews told The Washington Post that Area 51 is where, “we train American armed forces” and “is an open training range for the U.S. Air Force.”

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"The U.S. Air Force always stands ready to protect America and its assets," McAndrews added. She discouraged civilians from visiting the area.

Regarding the base's publicly-known history, Area 51 is a government facility in the Nevada desert near Groom Lake, a salt flat located about 120 miles north of Las Vegas. The site was chosen in the 1950s to secretly test the Air Force’s U-2 aircraft and train pilots, according to the CIA.

The area had earlier been used during World War II as an aerial gunnery range for Army pilots.

Employees take small, unmarked passenger planes from the Las Vegas airport to get to the remote area, according to Business Insider.

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President Dwight Eisenhower approved the facility’s development in the 1950s, according to the CIA. The site was used by the Air Force to test the U-2 spy plane during the Cold War.

In 2013, the CIA acknowledged its existence, releasing its location and how it had been used to test military aircraft, including the F-117A, A-12 and TACIT BLUE, according to Business Insider.

Fox News' Stephen Sorace contributed to this report.