A long-awaited Washington area branch of Maryland's federal court will be located in Beltsville in northwestern Prince George's County, the General Services Administration announced yesterday.

Hailed by Washington area lawyers as sorely needed and resisted by Baltimore judges as cumbersome and expensive, the $21.9 million facility will be built near Edmonston Road and Cherrywood Lane just outside the Capital Beltway on the grounds of the federally owned National Agricultural Research Center. The 115,000- square-foot building should be completed in late 1993, GSA said.

Officially called the southern division of the U.S. District Court for Maryland, the building will include seven courtrooms, plus space for a supporting staff of clerks, marshals, prosecutors, probation officers and others, said Chief Clerk Joseph A. Haas.

Up to now, the U.S. District Court for Maryland has been in a single building in downtown Baltimore. Most federal criminal and civil cases are tried there, regardless of what part of the state they originate from -- be it Baltimore, Eastern Shore, Western Maryland or suburban Washington.

With up to 30 percent of the caseload coming from the Washington area, Rep. Steny H. Hoyer (D-Md.) introduced legislation in 1987 to establish a southern branch of the Baltimore court in Prince George's County, which falls in his 5th Congressional District.

The measure required that the new court be within five miles of the Montgomery County boundary. It would be used for cases originating in Prince George's, Montgomery, Calvert, Charles and St. Mary's counties.

Washington area lawyers lobbied for the measure. But the court's nine federal judges -- all of them Baltimore area residents -- were unanimously opposed, saying it would create a clumsy and expensive double bureaucracy.

It also meant some judges would have to commute "35 miles and 45 minutes away," Chief Judge Alexander Harvey II said yesterday. "We had the facility here in Baltimore and didn't see the need for a new location." But "that's water over the dam now," he said in an interview, "and we'd like to see {the new court} get started."

Haas said the new building will contain a large ceremonial courtroom and two standard-size courtrooms for judges, plus smaller courtrooms for two magistrates and two bankruptcy judges.

He described the new court as a "full service facility" with complete clerical and other staffing. "Everything that's here {in Baltimore} will be replicated down there in smaller scale," Haas said.