NOTHING OF GREAT MOMENT has ever happened in Howard County, either before the Maryland Legislature created it by lopping off a piece of Anne Arundel County in 1851, or since. No battles or catastrophes to warrant monuments; no place where statesmen signed treaties to end world strife forever; George Washington doubtless slept there but no one thought it important enough at the time to record, so no plaques.

Howard County's "historic places" are gracious estates and solid old homes, monuments to modest, comfortable wealth and peaceful, easy living on fertile farms husbanding some of the most prized cows, sheep, pigs and horses in the nation. For three centuries there were few changes except the normal progress of tractors supplanting plowhorses, automobiles supplanting wagons. A few long-commute pioneers bought land and built homes.

And then came James Rouse.

It was in the mid-'60s, and he came unannounced. He was known in high financial circles as a banker, developer of shopping centers, renovator of decaying downtowns, but few Howard County residents traveled in those circles. All anyone knew was that a mysterious company called HRD was offering prices at least double the going rate for farmland in the center of the county.

Howard Countians may have been farmers, but they knew about gift horses, could do basic addition and subtraction, and they knew that they could buy bigger farms with better buildings "upcounty" with the money they were being offered. So most took it and ran.

Rouse and HRD (Howard Research & Development, it turned out) made public their ambitions for a planned city, complete with maps and charts and bankbooks to demonstrate that they could carry it through. The county commissioners knew about gift horses too, being mostly farmers, so they bought it surprisingly quickly, promised the zoning, and Columbia was born 18 years ago.

Today its population is nearing 70,000 of a projected 100,000; its main mall is bustling and the village shopping centers are thriving; its commercial corridors are exploding with construction, mainly of high-tech industries.

Success was immediate, with astonishingly few growing pains, with far less grumbling and no strife between the old landed gentry and the new concentration of population than anyone had foreseen. Mainly because Columbia is a city of modest, comfortable wealth and peaceful, easy living.

But don't read comfortable or peaceful as dull. Columbia buzzes with activity, most of it, except in the worst days of winter, outdoors. It is rife with joggers, bikers & hikers who can go short or long because most of the "green spaces" are interconnected. And most of those have picnic tables and other such facilities, especially around the three man-made lakes and Symphony Woods, the grounds around the Merriweather Post Pavilion, home to summer concert series and graduation ceremonies for the community college and most of the high schools.

Although Columbia is divided politically and structurally into villages, each with its own main activities area, the focus of activity is the Town Center, commonly called downtown. And the hub of the center is the shore of Lake Kittamaqundi. (About the only folks not catered to when Columbia lakes were designed were the fishermen; the shallow waters were stocked only with trash fish, on purpose, so mosquitoes are never a problem.) On the green slopes, on the docks, on the stone and concrete walks, on the wooden platforms, around the bandstand, under the canopy of the fountain, beside the flower beds, Columbians and visitors loll or stroll or dance, eating and imbibing goodies from the incumbent restaurants, bars and fast-food emporiums (the authorities are tolerant of alfresco imbibing when there's no trouble, and trouble is rare).

And they converse. Polls indicate that Columbia has a remarkably literate population -- 62 percent of its residents (counting kids, who probably will) have college degrees. And they read. The central branch library nearby probably has a higher rate of usage than any except college libraries. It averages almost eight books per withdrawal per card, returns in 91/2 days. Everything's friendly, the only people you shouldn't engage in conversation are those engrossed in books.

If you're out of reading and have laryngitis, you can feed the ducks and geese or check out a boat or go to the movies or the exhibit that shows all about how Columbia came to be what it is and what it will be.

Or you can visit the mall, about a quarter-mile uphill. Visit is the operative verb. Although the mall merchants have no complaints that business is slow, the pace of the place seems leisurely. Rare is the harried shopper, elbowing ahead, frowning at his list. The mall is filled with establishments that quickly produce the entire spectrum of foods -- from fried dough to croissants with escargots -- no one eats fast. Snackers take a bite and (yes, again) they converse. Especially around the fountains.

A common diversion for residents and visitors in Columbia is strolling or driving around giggling at the street names which some call unusual, some call cute, some call cutesy, like Tinkerbell Cul-de-Sac, Cloudleap Court, Catfeet Court, Spotted Horse Lane, Woodelves Way, Raindream Hill, Humblebee Road, Morning Mist Lane, Barefoot Boy . . .

If these nudge a literary corner of your memory, you're right. It's part of the system, according to the imp in charge of street names. Many villages and neighborhoods in Columbia are named after authors and poets -- (William) Faulkner Ridge, (William Cullen) Bryant Woods, (Wallace) Stevens Forest, just plain (Emily) Dickinson, (Samuel) Clemens Crossing -- and the street names come from their writings. The exception is Wilde Lake, named not after (Oscar) but after (Frazar), who was chairman of the board of Connecticut General Insurance, which bankrolled the project.

Columbia's constant activities seem spontaneous, but are carefully planned and run by the various village boards and, in downtown, by the Columbia Association, whose members never run short of excuses for celebrations.

"Do you know any other city that celebrates its birthday every year for a week?" laughs Mike Strauss, an HRD executive.

The party this year starts Friday, June 14, and formally runs through the following Friday, but there'll be plenty of the hardy who will stretch the festivities through the weekend of the 15th and 16th. There'll be parades, clowns, concerts, clowns, jugglers, clowns, dancing indoors and out, at least one long- distance run, clowns, acrobats, balloons, fireworks, skydivers, dancing bears, horses . . . food and drink everywhere. The animals in the petting (and feeding) zoo may get indigestion. The merchants in the Mall will grumble about all those activities keeping people outdoors, then they'll fill out their deposit slips. Someone will tip over a boat in Lake Kittamaqundi and scream for rescue until he discovers that the water is less than waist- deep.

For the next couple of weeks, there'll be a hiatus and Columbia activities will calm down to the usual quiet frenzy; then comes July 4, a Thursday that will lead to Friday and Saturday. Then, Bastille Day, then spillover from the Howard County Fair in West Friendship, and Labor Day, then the Renaissance Festival . . . . WHERE THE ELLICOTTS HELD SWAY

About six miles along U.S. 29 from Columbia, Old Columbia Pike splits off to the northeast and descends steeply, narrowly and curvingly to Ellicott City, one of the oldest factory towns anywhere.

Before Columbia, it was comatose; but for the fact that it was the county seat, it would have been moribund. The few mills left from its glory days of the industrial revolution had a brief resuscitation during World War II making Army uniforms, then relapsed steadily until the advent of synthetic fabrics and double-knits killed them. The only visitors to the town were people who had to go to court and photographers attracted by the quaint granite buildings built one above the other (many on stilts) into the sides of the chasm carved by Tiber Creek.

Now the urgencies of running an exploding county have brought new life. Main Street's old houses and shops have been converted to boutiques, curio shops, art galleries, restaurants, and above all, antiques shops.

At the foot of Main Street is the B&O Rail Station Museum, the restored terminus of the first line the B&O built out of Baltimore, a line that ultimately went on to Frederick and Cumberland and to Ohio. The railroad had been formed in 1827 by a group closely tied to Ellicott City's industry, headed by then elderly Charles Carroll of Carrollton, a signer of the Declaration of Independence.

The line was completed in 1838 and on August 28 the first trip out was made by an engine called Tom Thumb pulling a single car filled with VIPs. As it neared Relay House, a stagecoach headquarters, a gray horse appeared, pulling a rail carriage on the parallel tracks. It was an obvious challenge to race. As the horse pulled ahead, the Tom Thumb built up a greater head of steam and soon overtook and passed. Then a pulley slipped, and Tom Thumb groaned to a halt. It may have been the last time a horse won.

Drawings of this race, plus models and other memorabilia, are in the museum and the restored freight building. Archeologists are uncovering the old turntable between these National Landmarks.

Off main street, up Church Road, then Court Avenue, is the former First Presbyterian Church, built in 1894, which now houses the Howard County Historical Society and museum, open the first and third Saturday of the month, and every Tuesday, 1 to 4 p.m. Of special interest there are the maps, clothing displays and the drawings and sketches of Ellicott City when it was Ellicotts Mills, and booming.

The Ellicott brothers, John, Joseph and Andrew recognized that the swift stretch of the Patapsco River where Tiber Creek rushed into it was ideal for powering mills of the fledgling industrial revolution. In 1772 these inventive Quakers moved from Pennsylvania and began building. They convinced farmers of the area to switch crops from tobacco to wheat, developed and produced liming fertilizers to restore the depleted soil. They built forges and were soon producing wagons and carriages and textiles. Their patents included a four-sided clock. Documents indicate they designed, built and successfully tested a steamboat in 1789, but never patented or developed it. Support is building for collecting records and relics of their enterprises and housing them in the town named after them.

Also worth a stop are the original court house (about 1840) and the ruins of the Patapsco Female Institute, a boarding school for girls, and several fascinating old structures nearby. A brochure suggesting a walking tour of the area is free at any shop.

Not far from Ellicott City, along U.S. 40 toward Frederick, is the Enchanted Forest, a charming predecessor of today's theme parks. It is well maintained and its low-key quaintness entrances children and even parents. It's open daily through September 8, then weekends only through October 27. Call 301/465-0707. RAMBLING ROADS

The charm of the rest of Howard County is its beauty, especially the southern, western and northern parts, largely farmland. Rolling country, very fertile. An incredible number and variety of trees. Neat farmhouses and barns. Some people like to drive around blindly, knowing they won't get lost for long. But here are a few suggestions. The directions are necessarily detailed, because this is true shun-piking. If you think one glimpse of the water is enough, skip the next sidetrips. Similarly, with the parks and rivers. Note that these tours interconnect, so you can combine them, do them in parts. You might want to try them as navigation practice for road rallies. PLAYING TAG WITH ROCKY GORGE RESERVOIR

The Patuxent River is the boundary between Montgomery and Howard counties, and if you drive to Howard on I-95, on your left you'll see the dam that forms Rocky Gorge Reservoir. Take the next exit, Rte. 216, toward Scaggsville. Rte. 216 seems to deadend at a traffic light, but go left, still on 216, then sharp right, and almost immediately leave 216 left on Harding Road. You'll soon be looking down at the reservoir. After you have looped around a cove, you near Coon Manor. An unmarked road to your left takes you down to the water. Back on Harding Road, proceed to the intersection of Old Columbia Road. Straight ahead again takes you to the water, right takes you to U.S. 29.

Across 29, pick up Murphy Road, which winds and climbs to deadend at 216 at St. Paul's Lutheran Church. Across the road is the Iager family's Maple Lawn Farm, home to some of the top Holstein dairy cattle in the world. Note the pond, populated with Canada geese whose ancestors stopped by on migration several years ago, found it hospitable and stayed on. The farm also raises superb turkeys, sold fresh-killed and dressed at Thanksgiving and Christmas. If that appeals, stop in and reserve one now; it won't be too soon since they always sell out.

Go west on 216 a scant block, but straight onto Lime Kiln Road. Almost immediately there will be a road to the left that again takes you to the water. A bit farther on Lime Kiln on your right will be Mauck's meat market, a family enterprise. Everything on sale is local and prime and, if you want, cut to order. Suggestions: pork tenderloin and sausage and shoulder clod roast beef, a huge, tender party cut, boneless and not to be found in supermarkets.

Continuing on Lime Kiln, Reservoir Road on your left will again take you to the water. Lime Kiln then deadends at Browns Bridge Road (when many of the old roads in the area were named, apparently apostrophes hadn't been invented). Go right, across 216, to Hall Shop Road, right (be wary, several sharp curves) to Rte.32. Left briefly on 32, then right at Clarksville Middle School on Trotter Road, which dips and winds around feeders of the Middle Patuxent River, past stone walls and glimpses of handsome old homes, to Route 108. Right three miles is the northwest entrance to Columbia, Harpers Farm Road. RIGHT ON TO BRIGHTON DAM

On Rte. 216, where you've been before, head northwest across Rte. 108 at Highland, which has a couple of restored old places selling curios and antiques and where 216 suddenly becomes Highland Road rather than Scaggsville Road. You'll pass some pretty, small horse farms, and some small estates with startling houses. Then go left on Brighton Dam Road to the dam, which forms Triadelphia Reservoir. Cross the dam, into Montgomery County, and there's a park with picnic facilities and a Washington Suburban Sanitary Commission facility where you can rent a rowboat (no motors allowed) and get a fishing permit.

Return to Highland Road, northwest, then left on Triadelphia Road. You can take a left on Green Bridge Road to the water, which Green Bridge is now deep under. Continue on Triadelphia, which has bent to the northeast, then make a sharp left on Roxbury Road to where it splits to Roxbury Mill Road, but go right on Roxbury Road, then left on Dorsey Mill Road to Roxbury Mills Road (Rte. 97).

Go north on 97 to right on Old Frederick Road to left on Forsythe Road through the Hugg-Thomas Wildlife Refuge to Rte. 32. Across 32, Forsythe has become River Road. You'll go along the South Branch of the Patapsco then swing south to Rte. 32 again. Go south to Slacks Corner and left on Old Frederick Road (Rte. 99) to left (north) on Henryton Road to the state hospital, there left into Patapsco State Park, which has magnificent stands of white pine as you again drive along the Patapsco. DOWN ON THE FARM

Returning south on Henryton to Old Frederick, jog right, then quickly left (south) on Sand Hill Road, to Old National Pike (Rte. 144). Go left about 21/2 miles, then right on Folly Quarter Road. As you cross Carroll Mill Road, the University of Maryland Central Farm is on both sides. It's worth visiting. This farm used to be primarily for feedstuffs crops research, but the livestock and truck farming have built up there as the facilities on the College Park campus have closed and the farm on Cherry Hill Road in Montgomery/Prince George's counties closed.

Then continue south on Folly Quarter to where it joins Shepherd Lane and Homewood Road and swings right. Go right and the Franciscan Fathers Novitiate will be on your right. Worth visiting. Either Shepherd Lane or Homewood Road takes you to Rte. 108, which takes you to Columbia.