Sometimes historic milestones are less than obvious, as in the modest groundbreaking Monday for a larger commercial building to replace the smaller cinder block one used since the 1920s by the Cross family of Brandywine.

But looks can be deceiving, and the new facility for the R&D Cross Southern States store represents a big change, and not just for the family-run business that began in 1928. The store embodies many of the changes that are coming to largely rural, southeastern Prince George's.

Sure, it's still country south of Upper Marlboro. But that is because horses need lots of space, not because farmers are thriving. That's the good news and the bad news for R&D Cross: As the number of farmers declines, tobacco fields yield to horse farms, farm fences to paddocks, and tobacco barns to horse stables. It's an emerging new market waiting to be served.

"Since we have tapped into the fast-growing horse industry, our sales have more than justified the construction of a new nice building," said Sandra A. Cross, president of the family firm founded by her husband's father, Russell, and his brother, Lewis, 71 years ago.

The Crosses supply building materials for indoor arenas, barn stables, riding arenas and horse paddocks that are built by an Amish family from St. Mary's County. Beyond that, their sale of horse feed now far outstrips feed sold for cattle and hogs.

A whole room in their warehouse--itself a converted tobacco barn--is filled with different kinds of horse feed. In the fiscal year ending June 30, they sold about 800 tons of horse feed, compared with only 12 tons of feed for hogs and cattle. They employ 14 people and have annual gross sales of $2.8 million.

The new structure, expected to cost $300,000, will be 3,800 square feet. That compares with 1,000 square feet in the cinder-block building, which itself was doubled back in the 1940s. "We're excited," Sandy Cross said, "just to have a building with [an indoor] bathroom."

Her husband David A. Cross, 62, grew up in the business founded when tobacco farmers were the mainstay. The Cross family would buy the tobacco right out of the barns and then strip and pack it for sale to the Baltimore buyers who would come and truck it away.

"We used to strip tobacco in the store," he said. "Farmers would come in and didn't have anything to do, and they would help us strip tobacco in there and talk."

The Cross clan also raised its own crop but stopped a decade ago.

"It got so the business had grown so much, we didn't have time to do the farming," said Sandy Cross. Or, as her husband put it, "We stop fooling with 'bacca back in the '80s." Now, they lease their land to Roger Hyde, the last full-time tobacco farmer in these parts.

Although customers stop by the store on a regular basis, R&D Cross also delivers. With three trucks at its disposal, it makes 20 stops on a busy day. Last Thursday, that meant bringing fertilizer to farms, water softening salt to the Colony South Hotel, hay to a big commercial stable in Clinton and feed to a large horse farm in Aquasco. Over the years, the list of regular Cross customers has grown, from 75 when the business began, to 500 in the 1970s, to about 2,000 today.

Since 1935, R&D Cross has been a member of the Southern States farmers cooperative, which now has more than 600 stores in 18 states. The Richmond-based cooperative leases computers to the Cross firm, provides it with products to sell and maintains oversight of the operation.

Southern States, founded by Virginia farmers in 1923 to obtain higher quality seeds for their crops, is one of the nation's largest farmer cooperatives today, and representatives were among the 30 people at the groundbreaking.

Even with the Southern States link, R&D Cross remains, above all, a family business, with the third generation now firmly ensconced in positions of responsibility. Son Dave Jr. and son-in-law Richard Sedgwick are the managers, while daughter Susan Sedgwick is vice president.

Dave Sr. also is a manager. Sandy, 54, has been president of the corporation since 1986. The firm is set up as 100 percent female-owned so that it more than qualifies for minority set-aside programs, and R&D Cross supplies the county with such items as bags of Urea to apply to sidewalks during winter snowstorms.

The goal, Sandy Cross said, is to pass the business along to the next generation, to keep it in the family and on the same land.

She fondly recalls when 9-year-old Dave Jr. would be running the store by himself and ride his bicycle out to the fields to get help loading a customer's truck. She sees in the new building the future of the next generation.

"Can't you just see in 10 years our little grandson running around and putting things in people's cars? Like Dave Jr.," she said to her husband, referring to Kody Cross, now just 4. "We're so excited. I'm so excited. It's like--wow!"

Asked what the new building meant to him, Dave Cross said, "To me, it's gonna mean more work. I like for it to go through, but . . . " Prompted by his wife to say more, he added, "I'm just hoping it's going to increase business and all that good stuff."

"So you can have a business to pass onto the next generation," she added, "to provide a service to the community as well as an income."

"We've always been . . . always served the community," he said. "Faithful, honest. Just give good service. We hope to continue [to give] good service." Which, as a matter of fact, is the store's motto: "Serving the Community."

CAPTION: Sandra and David Cross in front of the store that has been used by their family since the 1920s. It will be replaced by a new building.