For getting above the crowd while getting around town in style, there may be nothing quite like becoming a Minneapolis skywalker.

A system of enclosed, carpeted pedestrian bridges -- skyways -- connects the second stories of buildings in every major downtown block of this tidy community of computer makers, corn shuckers and mineral miners. The skyway grid has become an increasingly important feature of the city, inspiring a dozen other U.S. communities to launch their own multimillion dollar skywalker projects.

Heated in winter, air-conditioned in summer, the swank aerial sidewalks, together with well-appointed, shop-lined corridors around the periphery of the buildings, or straight through them, form an upper-level, maze-like commercial arcade of stores, eateries and boutiques that surely is one of central business district America's best answers yet to the suburban mall.

Just ask Ruthie McDonald. She lives on the north side of Minneapolis, but when she wants to shop, visit, buy groceries or just rub elbows with people, she jumps on a bus and heads into town. When she alights, McDonald enters a building at the north end of the skyway system, climbs to the second floor and spends part of the day circulating above the heads of much of the community.

"I do maybe three miles a day," she said. "Get my exercise this way."

Retired for the past few years after more than two decades of work making computer components for TRW Inc., McDonald spends her mornings caring for elderly neighbors and friends at a center to the north.

But after she has helped serve the daily hot lunch and washed up afterwards, she's ready for her habitual round of shops and stores in the skyway system. "They all know me," McDonald said, exchanging pleasantries with a waitress at her favorite yogurt shop while buying a 60-cent cone.

She then guided a questioning stranger unerringly around the complex of corners, crossroads and nooks that make the newcomer to skyway life long for a ball of twine. After an exhausting trek south, McDonald reined in. "Almost nobody from up north comes down this far," she said. "They don't know the area."

On a normal business day, tens of thousands of Minneapolitans surge out of the new steel-and-glass shafts of the rebuilding downtown to join Ruthie McDonald, browsing and spending in weatherproof skyway comfort. This last fact is crucial: despite being no further north than Bologna, Italy, Minneapolis has a continental climate, making it Moscow's rival for having what it takes to chill the spirit. Five months a year, the mean temperature in Minneapolis is freezing -- or below

The heated walkways over the blustery streets below give a carefree note to the skywalkers' comings and goings. "It's warm -- that's the big thing," said a lawyer, a blur of pin-striped efficiency as he hurried from his office in one of the towers to a late luncheon date with a client at a restaurant a few aerial bridges away. "Who needs an overcoat?"

The Minneapolis system began in the grim days of the late 1950s, when shopping centers mushroomed in the suburbs while decrepitude and depression were turning out the lights in city centers. Amid derision and doubt, a local developer, the late Leslie Parks, built two skyways to connect his new office building with some other corporate buildings.

Little more than a local curiosity for some years, the bridges over Marquette Avenue and S. 7th Street steadily won adherents. Another bridge was added in 1964, three more in 1969, and four in 1973. The entire system took off with the buildings of the IDS Center, a square-block financial headquarters with a huge, glassed-in courtyard that serves as the skyway hub.

Now, 27 bridges link 30 blocks, with 13 more skyways to be completed in 1986. More than 80,000 apartment dwellers and office workers are tied into the system.

Initial worries that the bridges would cut into street-level commerce have faded. John Burg, a city planner, said the main downtown shopping area along Nicollet Mall "established itself as a retail center prior to the time the skyway system become popular. The mall continues to be the retail focus."

Across the Mississippi River in St. Paul, these developments did not go unnoticed. The Twin City now has its own skyway network covering 27 blocks -- 2 1/2 linear miles -- and tying in about 2,000 high-rise residents with a major department store and dozens of shops.

Crime has been minimal, officials of both cities say, although the St. Paul network may have more trouble because it stays open later than the Minneapolis grid, most of which is closed by 7 p.m.

Whatever the problems, they seem to be outweighed by the advantages. Des Moines, Dallas, Charlotte, N.C., and Cincinnati all have skyways and more are on the way elsewhere. Soon, there will be skywalkers across America.