IMPERIAL, Mo. (AP) _ Scientists have known for more than 150 years that huge, hairy elephants known as mastodons roamed the woods of eastern Missouri, but they learned of the presence of a more deadly species more recently because of four housewives.

The women campaigned to win park status for a patch of land threatened with development that was known to be the ancient stamping grounds of mastodons.

After their success, scientists moved onto the land about 20 miles south of St. Louis and discovered that man and beast had clashed there.

Archeologists found in the area a Clovis projectile point, a primitive arrowhead known to have been used by prehistoric man to hunt mammoths - a close relative of the mastodon - in America's Southwest and the Great Plains.

The evidence found here six years ago by staff of the Illinois State Museum was the first indication that Clovis man, who lived around 12,000 years ago, also hunted the mastodon as far east as Missouri.

''We have here some of the best evidence of hunting, of man-mastodon interaction, in the world,'' said Dr. Bruce McMillan, director of the museum in Springfield, Ill. ''But many questions remain, and more work will require further funding.''

The site, known as the Kimmswick Site, became an archeological park after Dorothy Heinze and three other women formed a committee to fight the proposed development.

The group bought the site for $568,725 with a $200,000 grant from the state, $300,000 from the federal government and the remainder from private sources ranging from county schoolchildren to the McDonnell Douglas Corp.

''The bones of more than 60 mastadons have been taken out of Jefferson County,'' said Heinze, secretary of the Mastodon Park Committee. ''We just felt it was time to preserve some of our heritage for our children.''

Contruction is to begin soon on a $1.2 million museum and interpretive center to display future finds.

Mastodon bones were first found at the site about 150 years ago by Albrech Koch, a free-wheeling entrepreneur who put together a skeleton and took it to Europe. ''The Missouri Leviathan,'' as Koch called it, was later sold to the British Museum, where it was discovered that it was made up of bones from a number of mastodons, adult and juvenile, and some other animals.

The largest of the complete mastodon skeletons since taken from the park area is on exhibit at the Smithsonian Institution in Washington.

Dr. Russell Graham, an archeologist with the Illinois State Museum, said the Clovis points, bones, tools and other items are being analyzed in efforts to learn more of what was going on around Imperial 12,000 years ago.

Mastodons were much like mammoths, but there were some significant differences, said Graham. ''Mammoths had teeth that looked like washboards and were suitable for grazing on grass in savanahs, large grassy plains. Mastodons had conelike teeth similar to our own. They were browsers and ate brush and leaves and lived in forested lands and meadows.''

At 425 acres, the 9-year-old Mastodon State Park is the state's smallest. But it has meant a lot of work to Park Superintendent Wes Johnson, who is building trails and stairways to make the boneyards accessible to museum visitors.

''We expect a lot of visitors when we get through,'' Johnson said. ''Now the world knows what we've got here.''