Last year nearly $19 million worth of alcoholic beverages was sold at two stores flanking the Maine border here. And one of them, New Hampshire State Liquor Store No. 38 calls itself the nation's busiest liquor store.

But besides building a busy trade and turning millions over to state government, the two stores are strong competitors because one is run by the State of New Hampshire, and the other, in nearby Kittery, is operated by the State of Maine.

In a battle that has become well known to natives, the two states are throwing lower prices and new stores at the booze-buying public. Taxpayers and customers are the apparent winners.

With more than 70 stores around New Hampshire officials there claims a 1977 gross of $118.2 million. That same year, Maine took in $56 million at two stores. The profits are poured into the states' general funds.

Both states estimate that a large percentage of their customers are from out of state, but New Hampshire seems to have a better handle on who's buying what and where the customers are from.

New Hampshire State Liquor Commissioner Costas Pentas says more than half the cars jamming the parking lot of the Portsmouth store seven days a week are from out of state. Most are from Massachusetts, Connecticut and Maine. On a recent sweltering day, three buses from Massachusetts, 20 cars with Connecticut plates and another dozen with tags from other states clogged the lot. The buses stop on a regular basis.

"You should see this place when it's really jammed," huffed a clerk busy restocking wine shelves. "Before Labor Day or any holiday, the lines go out the door. We have five or six people on registers and we just can't keep the shelves stocked. It's sort of funny, though, every time a busload of senior citizens pulls out, we have to restock the brandies and the sherries."

But although sales are brisker in Portsmouth, prices are lower in Maine. Retail prices for quarts or fifths average 5 to 10 cents lower in Kittery than in New Hampshire. Half gallon bottles sell for 15 to 90 cents less in Maine.

Maine Liquor Commissioner Aurele Bosse says "the intent of our Kittery store is solely to compete with Portsmouth. That's it. And we find much of our business is from New Hampshire people."

Maine may be drawing customers from across the border, but many Maine residents refuse to step in the Kittery store. They object to a state policy that allows lower prices in Kittery than any other place in the state.

To combat a flood of Maine buyers headed for the Granite State, Maine opened the Kittery store with discount prices. But every other store in Maine must sell at higher prices. For example, a half gallon of scotch that sells for $24.05 in Kittery costs $32.80 everywhere else in Maine.

"Sure, we get complaints by the barrelful about the discrepancy in prices," says Bosse. "But what we're doing makes good business sense. We can't afford to lower prices all over the state where we don't do the volume we have in Kittery. We would lose a lot of money."

Frank Robie, the commission's administrative assistant, estimates the loss would be around $7 million annually. "That's $7 million from the state budget that would have to come from some other source," Robie says.

"The idea of the Kittery store is to create competition. People are just beginning to know that we have lower prices. Law prohibits us from advertising so we just have to wait for people to find out about us themselves."

He adds, "The retail prices in our stores are set by the Legislature. They make it possible for us to charge lower prices only in Kittery. And the only way to change that situation is an act of the Legislature."

Robie and Pentas say that when people buy at their busy stores, "They aren't like the guy from Presque Isle buying himself a bottle," as Robie puts it.

The Portsmouth store has a tough time supplying enough shopping carts for its customers, while in Kittery "they buy by the case more often than not," he adds.

Historically, the New Hampshire stores have gotten most of the consumers' attention. The Granite State outlets are located strategically to sell to travelers headed for Maine, Vermont or Canada and back again. Pentas says the commission has won approval to build another store on the southbound side of Interstate 95 near the Massachusetts border. "That will make it easier for people traveling south who don't wasn't to drive about 20 seconds to get to the Portsmouth store," Pentas explained, laughing.

Pentas says the extra store probably won't hurt the Portsmouth one, which last year grossed $13 million. The Kittery store took in just half that.

Massachusetts officials have long been concerned about the dollars flowing out of their state and into New Hampshire liquor tax revenue to New Hampshire. In 1977, he ordered tax agents into New Hampshire to watch those coming out of liquor stores and headed over the Massachusetts border with more than the legal limit of three gallons of alcohol.

During that brief "liquor war," some of those tax agents were arrested by New Hampshire police. They were later released when police couldn't decide what to charge them with.

That row between the states died gradually, with Massachusetts withdrawing its agents and New Hampshire continuing to sell many times more liquor than its 800,000 people could consume. A clerk said the Ports-mouth store is so busy "that the Salvation Army lady stationed here always has a full tambourine."

And what about Maine?

They're moving along quite nicely, says Robie, continuing to quietly underprice every store in the East. Thet are "trying harder" says Robie. Number two has to.