By Emily Flitter

FERGUSON, MO. (Reuters) - Since looting first erupted following the August police shooting of black teenager Michael Brown, nearly all the businesses in a 2 square mile area of this St Louis suburb have had to board up. One exception - a Conoco gas station and convenience store.

At least a dozen stores have been set ablaze and others looted in Ferguson in racially charged riots since a grand jury on Monday cleared white policeman Darren Wilson in the shooting, which has torn apart this predominantly black Missouri city.

The unrest surrounding Brown's death has underscored the often-tense nature of U.S. race relations. But the gas station has stood out as a beacon, literally and figuratively, as nightfall has descended and chaos has reigned around it.

On Tuesday night, as police and soldiers took up positions in the parking lots of virtually every strip mall and big box store around it, the forecourt of the brightly lit gas station was busy with customers.

One, a six feet, eight-inch tall man named Derrick Jordan – “Stretch,” as friends call him - whisked an AR-15 assault rifle out from a pickup truck parked near the entrance.

Jordan, 37, was one of four black Ferguson residents who spent Tuesday night planted in front of the store, pistols tucked into their waistbands, waiting to ward off looters or catch shoplifters.

Jordan and the others guarding the gas station are all black. The station's owner is white.

Ferguson has seen a stark demographic shift in recent decades, going from all white to mostly black. About two-thirds of the town's 21,000-strong population are black. By some accounts, the Brown shooting has heightened racial tensions in the city. But not at the gas station.

"We would have been burned to the ground many times over if it weren’t for them,” said gas station owner Doug Merello, whose father first bought it in 1984.

Merello said he feels deep ties to Ferguson, and if the loyalty of some of his regular customers is any indication, the feeling is mutual.

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REPAYING A DEBT

At times, Jordan and his friends were joined on Tuesday night by other men from the neighborhood, also armed. None of the men was getting paid to be there. They said they felt they owed it to Merello, who has employed many of them over the years and treats them with respect.

"He’s a nice dude, he’s helped us a lot," said a 29 year old who identified himself as R.J. He said he, like the other volunteers, had lived a short distance away from the store for most of his life.

He carried a Taurus 9mm pistol in his sweatpants and drew it out to show another customer, an older man at a pump who was brandishing a MAC-10 machine pistol.

Missouri allows the open carrying of firearms. State lawmakers recently passed a law overriding any local ordinance that banned the open carry of firearms by people who have concealed weapons permits.

R.J. said on Monday they chased away several groups of teenagers rampaging through the area.

But they have also had a close brush with soldiers from the Missouri National Guard, who mistook them for looters, he said. The guardsmen, rifles raised, had handcuffed one man before Merello came outside the store to explain that the residents were trying to help, not hurt.

While the volunteer guards talked, a white SUV pulled up and a thin young man sauntered into the store. A few moments later, there was a commotion. Merello frogmarched the man out the store.

One of the armed residents, Sean Turner, showed the .40 caliber pistol in his jacket and told the man, "This is what happens if you try to steal from this place."

(Additional reporting by Carey Gillam, Editing by Ross Colvin)