You might not believe it, given the visit by Uncle George from Putney, Cousin Marie and her brood from Wapakoneta and your college roommate and his lady friend from Cucamonga, but Mount Vernon is the only major tourist attraction in Virginia that drew fewer visitors last year than in 1984.

That isn't to say that George Washington's estate is lacking for visitors, including the ones you drove down there. A total of 1,036,306 visitors paid for admission in 1985, according to a newspaper roundup, down 28,826 from the previous year.

"We believe that any time we get over 1 million visitors, we've had a good year," said James Rees, Mount Vernon's director of development.

The roundup of Virginia attractions, made by the Richmond Times-Dispatch, showed increases of 5 percent or more in tourism at Fredericksburg, Virginia Beach, Colonial Williamsburg, Stratford Hall, Luray Caverns and Lexington. Virginia's theme parks showed increases: 4.9 percent at Busch Gardens, near Williamsburg, and 2 percent at King's Dominion, at Doswell, north of Richmond.

Natural Bridge, Thomas Jefferson's home at Monticello and Jamestown Festival Park showed increases of about 2 percent, and Yorktown Victory Center stayed about even.

One caveat: Some places, like Mount Vernon and Colonial Williamsburg, keep track of visitors through ticket sales. Others, like Virginia Beach and Fredericksburg, can only guess.