Correction: An earlier version of this article incorrectly reported that Pennsylvania posted its first decline in slot revenue this past fiscal year. The first decline was in fiscal year 2013. The article has been updated.

New beverage servers prepare for the grand opening of the Horseshoe Casino in Baltimore. Its direct competition, Maryland Live, is only 12 miles away. (Yue Wu/The Washington Post)

In the Maryland casino wars, the latest weapon of choice is the billboard.

A Maryland Live billboard was clearly visible over the shoulder of Baltimore Mayor Stephanie Rawlings-Blake (D) as she stood outside the unfinished Horseshoe Baltimore a few weeks ago to unveil a street sign that read “Casino Way.”

By then, the 12-by-24-foot provocation, which read, “Over $10 billion in payouts and counting,” had been there for a year. It was one more way for the Arundel Mills casino to thumb its nose at its new rival from 12 miles away.

Horseshoe Baltimore, owned by Caesars Entertainment, at one point responded by dispatching a truck with a Horseshoe billboard to drive around Maryland Live’s parking lots.

On Friday, Horseshoe got its chance to show what Maryland Live is really up against. Live has an Asian gambling area? So does Horseshoe, complete with a hand-carved waterfall relief and custom carpet inlaid with orioles and black-eyed Susans (the official state bird and flower, respectively). Live has a poker room? So does Horseshoe, and it’s going to be a stop on the World Series of Poker circuit.

And although Maryland Live — owned and operated by the Baltimore-based Cordish Cos. — might have hundreds more slot machines, only Horseshoe has stocked outdoor smoking areas with them.

The real competition for customers begins at 9 p.m. Aug. 26, when Horseshoe opens to the public.

In the storied annals of casino rivalries, the Live-Horseshoe contest is small-time. It has yet to achieve the heights of one-upmanship that has lined the Vegas Strip with a copy of the Statue of Liberty, a pyramid, fake pirate ships and one ginormous resort after another.

But even along Route 295, the consequences for losing are high.

One regional monopoly after another has crumbled as casinos have proliferated. Delaware’s Dover Downs has seen its revenue fall since 2006, when the first casinos in Pennsylvania opened. Pennsylvania, in turn, posted its first decline in slot revenue in fiscal year 2013, due in part to increased competition from new casinos in Ohio and Maryland. And Atlantic City, Vegas’s former rival, now faces the prospect of four casinos closing by year’s end and the loss of thousands of jobs.

Maryland has four casinos. Horseshoe and MGM National Harbor, which is scheduled to open in 2016, will make that six. Two neighboring states also have casinos, including Pennsylvania, which now generates the second-largest amount of gambling revenue in the nation, behind Nevada.

In the new regional gambling wars, proximity has become the ultimate trump card. To overcome that, “you’ve got to give a reason to drive past another casino to go to your casino,” said David Schwartz, author of “Roll the Bones: The History of Gambling,” and director of the Center for Gaming Research at the University of Nevada at Las Vegas.

Poker dealers get training in Poke Room at Horseshoe on Friday. (Yue Wu/The Washington Post)

From Maryland Live’s opening in 2012 as the nation’s third-largest commercial casino, it has had a relatively easy time picking off Marylanders from casinos in Delaware, West Virginia, Philadelphia and Atlantic City. It controlled about 80 percent of the Maryland casino market in 2013, according to UNLV’s gambling research center. But with Horseshoe’s arrival, it will lose some of that geographic edge. A November 2013 study commissioned by the Maryland Lottery and Control Agency predicted that in 2016, Live’s slots revenue could decrease by 16 percent and table game revenue by 25 percent. And that study didn’t factor in the potential impact of MGM National Harbor, which will open at the other end of the Baltimore-Washington Parkway.

“It is playing chess on a different level,” said Maryland Live’s general manager, Rob Norton, who grew up in the industry.

Casino operators have no illusions that what they are selling is unique, said Oliver Lovat, an international market expert based in London. Slots are slots are slots. Instead, they strive to distinguish themselves in other ways. This has lead to a perpetual arms race that over the decades has involved $1 steak dinners, royal tiger habitats and botanical gardens. These days, it is more likely to revolve around dueling rewards programs that give perks to players the more they play. Horseshoe claims it has an advantage in that area because their members can use their points at other Caesars properties.

Over at Arundel Mills, Norton is not fazed. “We’re heading into an environment we are comfortable in,” he said.

He and his staff have been gearing up for the competition for weeks. Maryland Live recently unveiled the first million-dollar slot machine in the Northeast. That made for an awkward moment during a recent media tour of Horseshoe when a cameraman asked Horseshoe’s general manager, Chad Barnhill, if he had one. “No,” he said. “That’s at the other one.”

Live’s strategy also involves Harley-Davidson giveaways, slot tournaments and buying up ad space in the baggage-claim area at Baltimore-Washington International Marshall Airport.

And there is still the billboard down the street from Horseshoe. There is a great view of it from one of the casino’s new slot-machine-loaded balconies.