In the District of Columbia, local organizers of Hands Across America are worrying about crowd control and making plans to divert the line into the White House next Sunday if President Reagan decides to join the human chain at the last minute.

In Maryland, the populated route between Baltimore and the nation's capital is filling up fairly easily, but there's still a huge gap north of Frederick that so far has few takers.

"Some stretches have more cows than people," said Margaret Rubino, the Baltimore-based state director. The full route runs 156 miles through Maryland, and she is hoping Virginians will cross state lines to join hands.

With the May 25 event just eight days away, there is still a lot of skepticism about whether nearly 6 million people will turn up to hold hands and actually link two coasts in a fund-raising extravaganza for America's hungry and homeless.

But in the Washington region, spurred by unprecedented support from corporations, the 3 p.m. event is shaping up as more of a sure thing.

"The Mall and downtown area are gone, and I'm starting to assign places in Southeast," said Donna Brazile, Hands Across America's director in the District, ticking off a long list of local businesses, government officials and individuals who have purchased spots in the line.

By Brazile's calculations, it will take at least 35,000 people to form a single file procession along the District's 29-mile route, including the nine miles of "feeder" routes through Anacostia, Georgetown and Northeast. She said she expects many more people than that.

The D.C. route will block 243 intersections, with police stopping traffic for about 10 minutes. To both attract and contain the crowds, 17 staging areas have been set up along the route, each with its own band and other entertainment that will get under way at 1 p.m. At 2:15 p.m., people will be asked to start lining up to form the human chain.

So far, those paying $10, $25 or $35 to buy a place in line are about evenly divided between corporate sponsors and individuals, though Brazile said she expects individual donations to pick up at the last minute.

Mid-Atlantic Coca-Cola has purchased the area in front of the White House, donating the spots to District schoolchildren. First American Bank bought the section of the line around the Washington Monument. Local Jazzercise clubs "own" the Capitol, and National Tire World of Woodbridge, Va., has a big chunk of the Reflecting Pool. Radio station WJLA bought the front part of the Lincoln Memorial, while Xerox Corp. will take its employes to Washington Circle.

Church, school, veterans and antihunger groups, unions, and groups of District and federal government employes are filling in other portions of the route, which will wind through all eight city wards. In Southeast yesterday, Ward 8 schoolchildren -- buying places on the line for a quarter or more -- contributed some $4,000 to join Hands Across America.

The idea for a coast-to-coast human chain on behalf of America's poor was suggested more than a year ago by USA for Africa, the famine relief drive of "We Are the World" recording fame. Its celebrity organizers said they hope this venture will raise $50 million to $100 million for antipoverty groups at home.

"The compassion is always there in people, you just have to find a new way to tap it," said Ken Kragen, who manages the careers of Kenny Rogers and Lionel Richie when he's not masterminding fund-raising efforts.

Nationally, according to organizers, about 2 million people have purchased spots along the 4,152-mile route from New York to Long Beach, Calif. The line goes through 16 states, 556 cities and towns, three mountain ranges and two deserts. Kragen said the route was designed so that 65 percent of the country's population live within 100 miles of the line, and said the biggest anticipated gaps are in the Southwest deserts.

Closer to home, local organizers say there aren't too many gaps, mainly because supporters have come up with some rather ingenious ways of filling them.

In Baltimore County, for example, the Ladies of the Wind motorcycle club is taking part of the line and has been distributing literature urging others to participate. A junior high school student got a local bank to buy 40 places for a student council association, and a fourth grader raised $1,440 at his school, which is doing its own promotion of the event.

One problem occurred along Rte. 40 at the border between Harford and Cecil counties in Maryland after police told organizers they couldn't take the line across the Susquehanna River bridge. The solution: Scuba divers and boaters have signed up to provide their own waterway link.

"My sense is that the line will fill," said Rubino, 30, who needs 205,000 participants for the Maryland portion. "We were at a small town fair in Laurel last week and were just swamped with people wanting to join."

Rubino, who was deputy advance director for Walter Mondale's presidential campaign, said the Maryland State Police and merchants along the route have cooperated with the event's organizers.

State troopers, on paid overtime, will be stationed in squad cars every half mile, and state police are even considering painting a green, water-soluable line along the 156-mile route. Most business firms, gas stations and restaurants along the line are lending the use of their parking lots and restrooms.

Baltimore, in particular, has been a big booster of the event, according to Rubino, who wants the city "to look like Los Angeles during the Olympics."

Brazile, 26, who came to Hands Across America by way of Jesse Jackson's and then Mondale's campaign, said corporate support has been equally forthcoming in the District. Working out of a suite of offices on Pennsylvania Avenue donated by developer Oliver T. Carr, with telephone service donated by AT&T, furniture donated by Cort Furniture Rental and office and computer equipment donated by several firms, she and 17 others also get a regular paycheck every two weeks. Median pay: about $2,000 a month.

"I will drink Coca-Cola the rest of my life," she said, grinning in acknowledgment of the several million dollars in seed money that Coca-Cola, a major corporate sponsor, gave early on to promote and organize the event. Citicorp/Citibank came on board three months later, kicking in $3 million and making it easier for organizers' 67 offices around the country to approach local banks.

Locally, hardware magnate John Hechinger lent a storefront office in Hechinger Mall. The Downtown Jaycees incorporated the project into the Cherry Blossom Festival. Safeway Stores, a national sponsor, donated plants and office supplies and helped with promotional events. Yesterday, working with Brazile's office, the grocery store chain gave 25,000 pounds of nonperishable foods to the Council of Churches of Greater Washington for citywide distribution.

Whatever money is raised by next Sunday's event will be handed out based on recommendations from a panel of food and housing-care providers chosen by the board of USA for Africa. Hands Across America's state directors have been asked to nominate proposed panel members. About 60 percent of the funds will be earmarked for existing programs and emergency services; 40 percent will be used as venture capital.

Brazile said local groups already have started calling her to request some of the money. She said she recommended panel members from the District but won't have anything to do with distributing funds because all local Hands Across America offices are scheduled to shut down June 15.

Although some sponsors have long been involved in community service, the Madison Avenue-type publicity that corporations are generating in their Hands Across America endorsement has left more than a few people feeling uncomfortable about the commercialization of the project. A group of antiapartheid activists even tried, unsuccessfully, to get organizers to reject support from firms doing business in South Africa.

"I'm somebody who has done a lot of projects with no money," said Brazile, who helped organize the 20th anniversary March on Washington in 1983. "It's a lot better having money. But I think it has become embarrassing in this country to have some people in the community making money and not putting any back to help the poor, and I hope that after Hands, we'll have a consistent pool of support."