GARRETT COUNTY'S north- south mountains, rising straight up from the Potomac's streambed, were formidable obstacles to the flow of settlers westward into the Ohio Valley.

So, the roads skirted them north and south. The first major road west during the colonial era was built from Cumberland, across the northern edge of what is today Garrett County, by British troops under General Edward Braddock in 1755.

Following an Indian trail, they chopped a 12-foot road through the wilderness, through present-day Grantsville and Friendsville, then turning north along the Youghiogheny into the Ohio Valley.

When Congress authorized the first National Road in 1811, it tracked the Braddock Road as much of U.S. 40 does today. Evidence of the old Braddock trail can still be seen at Little Meadows about four miles east of Grantsville on the north side of U.S. 40.

For the National Road, the longest stone arch of its day was built over the Casselman River in Grantsville in 1813, and it still stands, next to the U.S. 40 bridge.

Grantsville (pop. 500) is a center for other historic structures, all of them on U.S. 40 on the east side of town.

Stanton's Mill, built in 1797, is the oldest operating grist mill in Garrett County and has been in the same family for six generations. Robert Bender, the current owner, says it is used today to custom-grind animal feed. The original grindstones, now imbedded in a retaining wall out front, have been replaced by electric-powered steel blades. But the original beams, axe marks and all, are still there.

Visitors to the mill can buy locally produced maple syrup. "My family has been getting maple syrup from the same Amish family for a hundred years," says Bender. The cost is $6 a quart; $11 a half gallon and $18 a gallon.

Other historic structures include the Penn-Alps Building (originally built in 1818), and the Casselman Inn, built in 1824. You can still get a room in the original building for less than $30. For reservations, call 301/895-5055.

GRANTSVILLE is in the middle of Mennonite and Amish farm country. For a special treat, take a drive along Dorsey Hotel Road -- a narrow, winding but well-surfaced lane through rolling upland farm country -- and bordering forests north of Grantsville. Dorsey Hotel Road turns north off U.S. 40 right beside the Casselman Inn.

Better yet, stop by the Casselman and pick up a copy of "A Driving Tour Through the Grantsville Community," which is available for 50 cents. It will lead you through the town and the countryside.