Early man did not carve in darkness. Most cave carvings - ancient petroglyphs chiseled on cave walls - end almost precisely where daylight bathing a cave entrance ends. When ancient carvings or drawings - the latter called pictographs - are found deeper within a cavern, it can be assumed that daylight once reached the spot.

Places where the Stone Age and far later ages left their mark provide some of the Interstate Highway's most introspective Quick Stops. And not only in caves but also on rock walls, former river banks, desert floors and rock outcroppings all across America.Rock artists, whether Stone Age man or pioneers herding their covered wagons westward, held one thing in common: They entrusted ageless rock to preserve and pass on to generations to come the words and pictures they deemed important.

More than 5,000 petroglyphs adorn the rocks of the Bureau of Land Management's Three Rivers Petroglyph Site in New Mexico. Comprising one of North America's largest displays of ancient rock art, the site - off Interstate 25 via Highway 70, some 35 miles north of Alamogordo - preserves the carvings and paintings of a culture believed to have existed between A.D. 900 and 1400. For information, phone (505) 525-8228. Open all year. No fee.

Far more recent in origin are Indian petroglyphs carved into the rocky banks of the Columbia River near Ginkgo Petrified Forest State Park, just off I-90 at Vantage, Wash. An easy trail from the park's interpretive center leads to the rock carvings. The park is open from mid-May to mid-September. Phone (509) 856-2700.

Hundreds of petroglyphs emblazon the red sandstone cliffs of Nevada's Valley of the Fire State Park, off I-15 via State Route 169 northeast of Las Vegas. The ancient writings span a number of ages from the early basketmaker people to later Pueblo Indian farmers. Phone (702) 397-2088. Open all year. No fee.

The sandstone bluffs of El Morro National Monument (morro means "bluff"), off I-40 via State Route 53, southwest of Grants, N.M., have proved irresistible to rock scribes through the ages. Here you can see the scrawls, scribbles and elegant artistry of those who, during more than 800 years, passed this way: Zuni Indians, Spanish soldiers and American settlers and adventurers.

Rising 200 feet from the valley it dominates, the monument's namesake - El Morro, a sandstone mesa - is scrawled with one of the nation's most varied collections of historical graffiti. A self-guided booklet, obtained at the visitor center and museum, translates many of the Spanish inscriptions, including a poem carved in 1629 and the 1605 scribblings of one of New Mexico's Spanish colonizers and later its governor, Don Juan de Onate. For more information, phone (505) 783-4226. Open all year. Entrance fee: $1 per person; maximum $3 per car.

Some of the nation's most controversial glyphs adorn the Heavener Runestone, a 12-foot-high, 10-foot-wide stone in Heavener Runestone State Park near Heavener, Okla., off I-40. Some scholars believe the stone's lettering to be ancient Nordic runes (alphabet characters) dating to about A.D. 1012. If true, the Runestone would award the discovery of America to the Vikings nearly 500 years before Columbus. Phone (918) 653-2241.

Much of prehistoric man's rock art is threatened by weathering and vandalism. Such was the case of the ancient rock art discovered in 1936 in a Montana cave. Now preserved as Pictograph Cave State Monument - a National Historic Landmark - the drawings decorate the walls of the largest of the monument's three caves, located some seven miles southeast of Billings off I-90.

From the interpretive area, a short, hard-surfaced trail gives you a close-up of Pictograph Cave's wall murals. Although the meaning of the pictographs remains unknown, archeological excavation of the cave's floor to a depth of 40 feet has uncovered nearly 30,000 artifacts including stone knives and human bones. From these, archeologists have surmised that Pictograph Cave was a frequent haunt of primitive man over thousands of years.

Most of its inhabitants were hunters, rather than farmers or pottery makers. Some used the cave as a burial place. Over the centuries, unknown primitive artists - using red, black and white pigments - painted the cave's sandstone walls with shield-bearing warriors, ferocious animals and humanlike figures. Open May through October; $1 per person.

Rock art, often neglected and defaced in America, is finding booming interest among scientists, scholars and weekend glyph-seekers. The American Rock Art Research Association, based in San Luis Obispo, Calif., has nearly 450 members. Currently before the U.S. Congress is a bill that would establish in Albuquerque, N.M., the first rock art national monument.

Among rock art's avowed protectionists is the nation's newly appointed secretary of the interior, Manuel Lujan Jr., a former New Mexico congressman. To Lujan, as to other glyph fanciers, rock art in its most historic form, is a national treasure.

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GETTING THERE. Pictograph Cave State Monument: Leave I-90 at the Lockwood Exit, just east of Billings, Mont. Drive south seven miles following signs, to the monument.

FOR MORE INFORMATION. For a brochure, write Montana Deptartment of Fish, Wildlife and Parks, 1125 Lake Elmo Drive, Billings, Mont. 59105; phone (406) 252-0730.