Maryland Day, an official state holiday to be celebrated tomorrow, commemorates what Maryland historians call "the significant single event in the history of the state-its founding."

Libraries, courthouses and most state and county officers are closed for Maryland Day, but even state and county officers have trouble remembering why.

"Maryland Day?" Asked Gene Oishi, the governor's press secretary. "I've never heard of it. Is it something the governor is proclaiming or what?"

Celebrated officially for 63 years, Maryland Day marks the moment in 1634 when the first settlers docked the Ark and the Dove on the shore of St. Mary's County, proclaiming a new, and more tolerant, colony for England.

It is a holiday with less than a mass following . "It's one of our two weirdo holidays," explains former Acting Gov. Blair Lee III. "The other one is called Defenders' Day. That also pops up at you."

Lee, one of the few politicians who could pinpoint the purpose of the holiday, is not going to celebrate it.

Neither is William Amonett, chairman of the Prince George's County Council. "We've got entirely too many holidays. It's not that I'm not proud of Maryland. But I've been a businessman. I'm used to working."

But even the most obscure holiday has its staunch defenders. When Del. Robert Jacques of Montgomery County introduced a bill last year to get rid of Maryland Day, arguing that the closing of the government for a day would cost more than $4 million, "I got 700 calls in two days, complaining. I said to one of the callers 'What does Maryland Day mean to you? A paid holiday,' he said."

Jacques lost the last election. "Holidays have become shopping excursions. If you went around the streets of Rockville interviewing 100 people, you wouldn't find one who could tell you the significance of Maryland Day."

Gov. Harry R. Hughes will participate in the one actual ceremony celebrating Maryland Day, when the Dove, reconstructed at a cost of $200,000, will dock at St. Mary's City. A parade to Leonard Calvert Monument in Trinity Churchyard will culminate in a wreath-laying. Then the governor and the legislators will move to the reconstructed statehouse, where they will have a symbolic session of the legislature. However, all of this will take place today, on the day of the landing 345 years ago, but most of the state will commemorate the occasion tomorrow when public services will be curtailed.

"The governor's staff gets no holiday," said Oishi. "That's why we have no time to read up on Maryland history."

While Oishi said that children will be encouraged to wear the state colors, although he was not sure what they are (black and gold), schools will remain open throughout the state. There will be no statewide effort to commemmorate Maryland Day in the schools.

It's one of those things that may typically come up in a social studies class," explained spokesman Ken Muir of the Montgomery County public schools, who added that, as holidays go, "this one pales to Lincoln's Birthday."

Ed Papenfuse, the state archivist, is unhappy at the current obscurity of the holiday, especially in the schools. "Maryland Day does not get as much publicity as it ought to. It's equivalent to the landing of the Pilgrims at Plymouth Rock or the founding of Jamestown

"It is simply not emphasized enough in the school system," Papenfuse said. "My son, in second grade, is not exposed enough to the history of the state."

Papenfuse said he will celebrate Maryland Day by telling his children what it is.

But the schools are not entirely to blame for the general ignorance about the holiday. "Let's face it," Jacques said. "Maryland has a very transient population."

Allan Percival, a spokesman for Suburban Trust Banks, agreed. "Probably 20 years ago, Maryland Day was quite well celebrated. The banks used to close. Now, not enough people know about it."