To the north, there's Baltimore, the revitalized port city with a hard-working middle class rallying behind a rejuvenated baseball team and struggling to support an abysmal football team. Both play in an undersized and deteriorating stadium that lacks sufficient parking.

To the south, there's Washington D.C., the Nation's Capital, and its surrounding suburbs, filled with baseball-starved white-collar professionals seeking an easier way to see the Orioles and searching for scarce Redskin tickets.

Bringing the people of the two cities together, in a large-capacity stadium off Interstate-95 halfway between the two cities, would be a sports financier's dream come true. A Baltimore-Washington megalopolis would be the fourth-largest media market in the country (behind New York, Los Angeles and Chicago), with more than 5 1/2 million people, two professional football teams and a contending baseball club. Add horse racing, and the sports complex could rival the Meadowlands in New Jersey.

Among the persons who have given this common-market concept serious thought is Jack Kent Cooke, millionaire owner of the Washington Redskins and business partner of Baltimore Orioles owner Edward Bennett Williams. Last week Cooke said of such a possibility, "I'm thinking about it," lending new credibility to the idea of a Baltimore-Washington regional sports center.

Since then, Cooke, who built the Los Angeles Forum and owns the Chrysler Building in New York, hasn't said anything about the idea and has declined to elaborate.

The naysayers on both sides of the parkway can list a hundred reasons why the idea of a shared sports complex is impossible and imponderable, given today's tight money markets and the rivalry felt by the residents of the two cities.

But even the skeptics concede that if Cooke wants to build it, the Baltimore-Washington sports stadium could become a reality. Cooke can do it. The possibility has sent the Baltimore-Washington corridor into a paroxysm of conjecture, with businessmen, media agents, politicians and sports enthusiasts debating the potential and the risks of such a massive undertaking.

To build such a complex, Cooke would have to move his Redskins from their 55,000-seat home at Robert F. Kennedy Stadium, as well as secure commitments from Williams' Orioles, Robert Irsay's Colts and possibly a North American Soccer League team.

The Washington-Baltimore region as a single market is not a new idea. An organization called the Washington/Baltimore Regional Association, comprising prominent business leaders from both cities, concluded that residents of a regional common market would have a median income of $23,000 -- the highest in the nation -- as well as three major airports, 60 institutions of higher education, and a highly skilled population connected by two beltways.

Logic dictates that a centrally located sports complex would best serve both communities. Kick and scream as they may, citizens of both cities have to face the fact that urban sprawl is bringing them closer together. Abe Pollin, the owner of Capital Centre, as well as the Bullets and Capitals, said, "In years to come, I think it will become one big metropolitan area."

"You can make a good point that Baltimore and Washington are merging and will someday be a major megalopolis," said Washington advertising executive Earle Palmer Brown, an officer of Rosecroft Raceway, a harness racing plant. "If you put Baltimore and Washington together . . . you would have a major port, plus the economic stability of Washington, D.C. The concept of Baltimore and Washington as a single market is very valid."

The potential stadium site would be in Laurel, about 17 miles from Washington and 19 1/2 miles from Baltimore. Owners of Laurel Race Course, who have been trying to sell the track, had entered into discussions several weeks ago with lawyers from both Washington and Baltimore, including the law firm of Orioles owner Williams.

Those lawyers were representing some unnamed clients, according to Laurel Race Course President John Schapiro. The negotiations were cut short when Schapiro asked to speak to the buyers in person. "We couldn't take the negotiations very seriously," Schapiro said. "If somebody wants to make a deal, then the principals should sit down together."

Cooke denies that he wants to buy the track, but said last week that his interest lies in land nearby that could be used as a stadium site.

Laurel often has been mentioned as the site for a joint Baltimore-Washington stadium. The race track could be incorporated into the plan, which would be similar to the Meadowlands complex in New Jersey. Meadowlands lured the Giants football team out of Yankee Stadium and is courting the New York Knicks of the National Basketball Association and New York Rangers of the National Hockey League --both dissatisfied with the high rents at Madison Square Garden.

Schapiro hired a well-known Philadelphia-based real estate firm to conduct a site study of the 357-acre race track to determine the best use of the land. According to Charlie Seymour, the researcher at Jackson-Cross Co., which conducted the study, "I told Mr. Schapiro that I think a stadium is probably the best use of that site. It's accessible by rail, as well as by a highway network."

Laurel Race Course, situated midway between the two cities, attracts about 63 percent of its patrons from Baltimore and the rest from Washington and its suburbs, Schapiro said.

"I think we're ideally located in the corridor between Baltimore and Washington. We are doing a fine job in attracting people from the Washington and Northern Virginia area."

A single sports megalopolis at Laurel would result in two radio and television markets for the three major league teams that would play there. On the average, major league baseball teams derive about 20 percent of their revenue from radio and television rights. The bigger the market, the higher the proportion of revenue from broadcast rights, and the higher the profits for the franchise.

When Pollin decided to build Capital Centre in 1972, he considered building it along I-95 between the two cities. "We did some studies," said Jerry Sachs, president of Capital Centre. "We were concerned about locating a franchise neither in Washington nor Baltimore but in between, a franchise that would have the identity of neither."

Williams again raised the possibility of building a facility along I-95 almost two years ago, when he first purchased the Orioles from Jerold C. Hoffberger. Williams' flirtation with that notion in 1979 led to a storm of protests from Baltimoreans who wanted their team to stay in the city, and produced numerous bills in the state legislature to renovate Memorial Stadium in Northeast Baltimore.

"You have to look at it not as an abstraction, but as a concrete idea, the time for which is not right," Williams said. "The economics are totally forbidding. The interest rates where they are, the difficulty of acquiring financing makes it an astronomical project. I don't think it'll wash economically. I don't think it's possible in the private sector."

Don Poss, executive director of the Metropolitan Sports Facilities Commission in Minneapolis, which is overseeing the construction of the Hubert H. Humphrey Metrodome, agreed that a sports complex cannot be built without public assistance. The projected cost of the Humphrey Stadium is about $70 million, with $55 million raised through a public bond issue.

But economics also dictate that something has to give. The Colts are averaging only 28,000 fans per game. The Orioles averaged 9,750 fans per game during the 1981 strike-shortened season. Under their current broadcast contract, the Orioles receive about $1 million a year, one-fifth the amount of the New York Yankees. RFK Stadium, which is leased by the Redskins until 1990, can seat only 55,000 people. The 7,000-8,000 fans on the Redskins season-ticket waiting list might not mind the trek to Laurel if it meant they finally would get seats.

"They (the Colts and the Orioles) have got to look for ways to expand their revenue," said Michael Douglass, vice president and general manager of Washington radio station WTOP, which broadcasts Orioles games here. "Speaking purely as a fan, I'd like to see Baltimore have their teams and Washington have their teams. But as the general manager of a radio station that serves both markets, we'd like to see teams in a central location."

"If I had to make a decision, I'd make a business decision," Douglass said. "Let's face it, it's a business."

The possibility has aroused some old tensions between the two cities. Baltimoreans would have the most to lose if their Colts and Orioles moved 35 miles down I-95, simply to be more convenient to Washington. And there are many Washingtonians for whom Redskin football on Sunday afternoons is a religion.

"You're talking about a team that has a relationship with this city," said Annette Samuels, press secretary to D.C. Mayor Marion Barry. Samuels pointed out that the Redskins' current lease at RFK Stadium runs until 1990. "The mayor does not want to see the team leave, and he will enforce the lease."

"We think there's no reason for it, and we think the people won't drive that far to see their teams," said Chris Hartman, spokesman for Baltimore Mayor William Donald Schaefer. "We think it's a pipe dream. The Orioles and the Colts aren't going anywhere."

Critics of the concept often mention the age-old rivalry between Baltimore and Washington, and how the two cities would never agree to meet each other halfway. Civic chauvinism, they say, is deeper here than in places such as Minneapolis-St. Paul, where the two cities are separated only by a river, or in Dallas-Fort Worth, where "they are all Texans and they all have the same interests -- oil and cattle and money," said Harry Shriver, president of Baltimore radio station WFBR.

"Baltimore and Washington are only 35 miles apart, but they are 3,000 miles apart in life style," said Andy Ockershausen, executive vice president of Washington radio station WMAL-AM, which broadcasts Redskin games. "Baltimoreans are Baltimoreans and Washingtonians are Washingtonians. People are very territorial, especially in this market."

Ockershausen said, "Baltimore-Washington is not like Dallas-Fort Worth. Dallas and Fort Worth were always referred to with a hyphen."

"Baltimore and Washington are like the Army and the Navy, the Blue and the Gray," said Washington sports publicist Charles Brotman. "We are two separate entities entirely. We are rivals. We've been rivals."

"I just think it's oil and water, those two cities," said Mike Trainer, who as Sugar Ray Leonard's manager has been involved in several major sports promotions the past few years. "New Jersey considers itself a suburb of New York. Baltimore is not a suburb of Washington."

Changing a fan's habits, everyone agrees, is a serious marketing problem. Capital Centre, for example, spends only 5-10 percent of its promotional budget in the Baltimore metropolitan area, according to Sachs. Only 10 percent of the Bullets' fans commute from Baltimore, their former base.

This points to one of the risks a southern migration would have for both the Orioles and Colts, who have a sizable following in southern Pennsylvania and the surrounding Maryland counties. Schriver said, "Southern Pennsylvania, especially York County, is a tremendous sports market for Baltimore. Would they drive the extra 35 miles to Laurel? If I were in the sports business, I'd have to research how many fans I could pick up from Northern Virginia to compensate for all the fans I would lose from southern Pennsylvania."

Marlin (Curley) Holtzapple, the court clerk for York County and former shortstop for the Baltimore Orioles, has season tickets for the Colts, as do nine of his Pennsylvania buddies. They also go to Oriole games. "Now we can sit around and say, 'What are we going to do tonight?' and the baseball game is only an hour away," he said. "If they move it, it'll be two hours away. There's no way we'll drive two hours to a game."