After years of effort, Maryland's black legal community finally succeeded today in having one of its number appointed to the state's highest court.

Harry A. Cole, a 56-year-old Republican who has served as a judge in Baltimore City's trial courts, will become the first black in Maryland's 200-year history to sit on the Court of Appeals.

When Cole first entered Baltimore City politics more than 30 years ago, neither the city bar association nor the Maryland State Bar Association would admit black attorneys. And it was through membership in these groups that state judges were appointed.

However, in the intervening years, these restrictions were abandoned. And the state's black electorate, although it is seldom organized enough to vote as a bloc, has become an important force in Maryland politics. And Maryland's Gov. Blair Lee III, who today appointed Cole, is running hard for election as governor in his own right in the 1978 elections.

All leading black politicians in the state, including U.S. Rep. Parren Mitchell of Baltimore, head of the congressional black caucus, had made repeated and strenuous calls for the appointment of a black to the Court of Appeals.

Nevertheless, according to at least one Lee aide, Lee's desire to appoint a black attorney to the court was based at least as much on personal conviction as on political considerations.

And Cole, a Republican who in 1954 became the first black ever elected to the state Senate, was clearly not Lee's first choice.

After the state's 13-member judicial election committee gave Lee a list of five lawyers which it said it would recommend for appointment to the Court of Appeals - a list from which Lee is virtually forced to choose under the existing rules - Lee openly chastized the committee for not including the name of Joseph C. Howard among their selections.

Howard, a controversial civil-rights activist who is also a judge on Baltimore's Supreme Bench, has a substantial following among Baltimore's black politicians.

However, when announcing Cole's appointment today, Lee refused to dwell on the subject of his annoyance with the selection committee, and said that it had taken him nearly six weeks to make the appointment "because I was thinking about it."

At the conference, Lee called Cole a "level-headed, thoughtful man," shortly after saying, "I've appointed Judge Cole and I wouldn't want to demean him in any way. He's a fine guy."

When Cole was asked this evening about Lee's repeated comments in the last month indicating his preference for Joseph Howard, Cole merely replied, "No comment." After a pause, he added, "You don't bite the hand that feeds you." Cole had earlier remarked that he was "delighted with the confidence the governor has expressed in me."

The selection of Cole and the additional appointment of Ellicott City lawyer Arnold J. Hopkins as director of the State's Department of Parole and Probation left Lee with only one major vacancy to fill - the cabinet-level secretary of the Department of Economic and Community Development.

Lee made it clear at his press conference today that he would like to give that job to Henry G. Parks Jr., a black businessman who founded Parks Sausage Co. Parks, however, appears to have taken himself out of the running for the post.

If Lee had been able to appoint Parks - thereby having at least one high-level black appointee to his credit - he might not have felt obliged to select Cole for the Court of Appeals job, according to one Lee aide.