Traditionally, the Christmas shopping season begins the day after Thanksgiving. And the City of Frederick, just 45 miles north of Washington's, isn't about to change that. In fact, it's adding to the seasonal surge this year with the first Maryland Christmas Show, Friday, Saturday and Sunday at the Frederick Fairgrounds. There'll be four buildings crammed with mantels, doors and windows decorated for the season, trees trimmed to the tee, a stocking competition display, Christmas ornaments and handcrafted items, country jellies, smoked meats and such, not to mention the round guy in the red suit taking kiddies' orders. Admission is $3 for adults; $1.50 for children six to 12; under six are free, as is parking. To get there, get off I-270 north at Route 85 north (exit 1-B) to South Market Street and follow signs to the Fairgrounds. Call Tourism at 301/663-8703.

* You'll get a further feel for an old- fashioned Christmas in Frederick when you hop aboard the 40-seat open surrey pulled by draft horses and guided by a driver in top hat. Historical carriage rides begin this Friday and run through December 23. Adults $2; 12 and under, $1. Hours: Monday-Friday, 6 p.m. to 10 p.m.; Saturday, noon to 10 p.m.; Sunday, noon to 5 p.m. 301/662-6727.

* In Brunswick, Maryland, not quite so far north, the Christmas season kicks off in Victorian style as this picturesque railroad company town decorates the three-story Brunswick Museum in a turn-of-the-century style. There'll be an HO-scale model railroad running over a third of a mile, and a Santa's Christmas Shop. Brunswick stew and homemade bread will be on sale. Hours: Saturday and Sunday, 10 a.m. to 5 p.m. Admission is $1 for adults; 50 cents for children and 60 and older. Take I-270 to U.S 340 west to Route 17. Call 301/834-7100 or 834-8400.