However, most did not attempt to enter the site, long rumoured to house secrets about extraterrestrial life. A festive scene emerged around 3am local time (10am BST) on Friday, the date and time a Facebook user had jokingly invited people to run into the base on foot.
The event’s details section stated: “We will all meet up at the Area 51 Alien Center tourist attraction and coordinate our entry.
“If we naruto run, we can move faster than their bullets. Lets see them aliens.”
Naruto is a reference to a popular Japanese anime character.
Among the UFO enthusiasts and curiosity seekers, one man wore an orange space suit and some sported tin foil hats and alien masks.
A sign in the gathering read: “Free ET from the government.”
One young woman ducked under a protective gate and was briefly detained by authorities and released.
Others stayed outside the perimeter, according to law enforcement officials keeping watch over the crowd.
Orlando Guerra of the Nevada Department of Public Safety Investigation Division: “They’re just here to see what’s going on. In fact, they’re here to have fun.”
The US government did not confirm the base existed until 2013, when it released CIA archives saying the site was used to test top-secret spy planes.
The documents, however, did not end suspicion about space aliens there.
Area 51 sits about 12 miles (19 km) from Rachel, Nevada, a tiny outpost north of Las Vegas that is hosting a music festival to entertain any UFO hunters or others heading to the region.
Some residents had urged the public to stay away because they worried the town of 50 year-round residents would be overwhelmed with unruly tourists.
As of early Friday, a few hundred campsites had been set up by visitors outside the Little A’Le’Inn, an alien-themed motel and restaurant that is Rachel’s only business.
Connie West co-owner of the inn, who had scrambled to set up a campground, bring in portable toilets and otherwise support the influx of visitors, said: “I’m relieved it’s here.
“It’s happening. There was no stopping it.”