BEAVERTON, Ore. — View-Master amazed a generation of American kids by transporting them into a wondrous 3-D world through a cheap plastic machine.

But as electronic toys gained prominence among children — and even adults — the popularity of the View-Master began a gradual decline after its heyday in the 1970s. With teens and preteens today getting their thrills from the Internet and video games, analysts say View-Master's remaining enthusiasts are primarily young children.

Later this year, Mattel Inc. will close the Beaverton, Ore., plant where the 60-year-old toy has been manufactured for more than three decades, lay off all its workers and move production to Tijuana, Mexico.

The move will leave Etch-A-Sketch, hand-produced in Ohio, as the last baby boomer mechanical toy still in production in this country, said Chris Byrne, editor of the Toy Report, a New York newsletter for the toy industry.

"By many standards, it's very low-tech — but it's still magical," Byrne said of the View-Master. "It was a cool thing to have."

Mattel will not disclose sales figures for the View-Master line, and Byrne said the industry did not have a good estimate.

"But you can bet they wouldn't keep making them if they weren't profitable," he said.

Over the decades, national parks, Disney characters, movie stars, the moon landing and even Michael Jackson in all his "Thriller" creepiness have come to life on the little 3 1/2-inch-wide reels that fell into place with a satisfying click of the tough, spring-loaded lever in the patented stereoscopic viewer.

"I always thought it was a good, clean toy," said Ken Purvine, who spent 36 years at the View-Master plant in this Portland suburb. "You could just turn it over to your kids and watch them have fun."

The company, which has gone through several changes of ownership, was founded in the summer of 1938 when William Gruber was visiting the Oregon Caves National Monument and — literally — almost ran into Harold Graves, president of Sawyer's Photographic Services.

Gruber was using a special camera he had rigged for stereo photography, and Graves saw a potential business opportunity. The pair formed a partnership to produce the first View-Master in 1939 in Portland.

The viewer that became so popular with children, however, was originally intended as an educational tool for adults.

During World War II, the military used the 3-D viewers for training and purchased 100,000 of them, along with nearly 6 million reels between 1942 and the war's end in 1945.

The market for the sturdy little viewers expanded with the baby boom.

In 1951, Sawyer's purchased the Tru-Vue Co. of Rockford, Ill., which produced stereo filmstrips, eliminating View-Master's only serious competitor for children's attention while also acquiring rights to Disney characters.

Scenes from popular movies, and later TV, were made into stereo reels, hundreds of "scenics" of national parks and world travel were produced, and advertisers ordered special runs to feature their products, according to Dan Nottage, Mattel general manager for Oregon.

In October 1966, View-Master was purchased by General Aniline & Film Corp., or GAF, which made slide and Super 8 movie projectors.

"I still remember Henry Fonda pitching it for GAF," said Sean McGowan, a toy industry analyst for Gerard, Klauer & Mattison in New York.

The toy prospered, he said, because so many different companies were happy to license photos for the View-Master reels, knowing they would be snapped up.

But GAF saw its profits fall as the age of electronic toys and the computer began.

The decline of the View-Master may also have been due to a shrinking age bracket for its market, now closer to kindergarten age rather than extending up through 10- to 12-year-olds, McGowan said.

"It's probably the quintessential example of 'age compression' in the toy industry," he said.

"Kids are more sophisticated culturally, socially and technologically," McGowan said. "The sophistication is such that products that kept 10-year-olds enthralled years ago no longer cut it."

View-Master was sold to businessman Arnold Thaler for $24 million in 1981, who six years later purchased Ideal Toy Co. to create View-Master Ideal.

Then, in 1989, View-Master was sold to Tyco Toys of Mount Laurel, N.J., which merged with Mattel in 1997.

The Beaverton plant employed up to 2,000 people during its peak production years in the mid-'70s, but it now is down to about 60 people. Layoffs were announced in February in preparation for the official closing, expected before the year ends.

"It's sad to see it leave the U.S.," said Ruby Peterson, who has been on the View-Master production line since 1961.

"It was very exciting to make the viewer," she added, "to think that we're the only place in the United States to make it."