What becomes a living legend most? For Charlotte Sheffield Maxfield, the Utahn who became Miss USA in the Miss Universe Contest of 1957, it's a giant collection of authentic costumes - enough to play dressup nonstop for about a month.

Most of the year, the collection is stored under lock and key. But at Halloween it oozes up from the basement to drape the living room furniture, mantel and piano, hang from the doorways, perch on the lamps and cluster in every corner, spilling over into the kitchen and hallway.Maxfield lends the clothes through her little cottage industry, The Authentic Bargain Costume Service, but she has no desire to run a commercial costume shop. She calls herself a private costume consultant, and she does not have a set rental fee. She helps people by appointment, asking what they always wanted to be, and what they feel comfortable paying, according to income.

She suggests other costume dealers for wigs, makeup and yardage. "In turn, people are often referred to me for authentic national or antique vintage clothing, complete with shoes, hats, and jewelry," she said. For an appointment, call 272-5357.

Indeed, Maxfield doesn't feel one bit commercial. "I think of myself as doing a service. It's something I can do 'til the day I die, and it's so much fun," she said. "My family can borrow whatever they want free. So far I have mostly served friends, relations and neighbors, and those whom they refer. I just did my pregnant daughter-in-law as Pocahontas! And I dress whole groups of my children's high school friends for the Monster Mash. They might be Mafia and flappers, or belly dancers and sheiks, or south of the border couples."

Maxfield first took her costumes public nine years ago, as Charlotte's Attic, in a pioneer mansion on Seventh East where the family then lived. "I love to be creative. I do very little sewing, but I have a feeling for how things can be put together for an outfit," she said.

She finds that costumes go deeper than just pretty clothes; they are a form of living history, and a great people-to-people connection. Interest first stirred in her when she traveled the world as Miss USA.

"I had three ways of bringing a little of a foreign country home with me," she said, "A song in their language, a dance and a costume." She first bought a Czech doll, and had the clothing copied in the U.S., since visitors were not allowed to bring out the costumes. She also gained a deep, abiding thankfulness for living in free America.

Charlotte has made good use of tours abroad, as a member of the Mormon Tabernacle Choir. She's become known as "the costume lady," and friends and acquaintances help her spot potential shopping places. "My luggage is filled with tightly rolled finds, and my carry-on is really a drag-on," she laughed.

For example, on the Choir's 1980 Scandenavian tour, she bought dresses in Copenhagen and Malmo, Sweden, from the period of her great-great-grandmother. One is brown, one sagey green, and both are a little faded, but the firm, silky gabardinelike material is still sturdy and firm, and lacework at the bosoms had been carefully reconstructed. "Women in those days had only one good dress and one pair of boots," she explained, "so they usually bought first quality.

"I haunt antique stores and `trendy' shops, and thrift stores. In Australia I went through the `Good Sammies' (Samaritans). People are beginning to donate me `grandmother's trunks,' knowing I will refurbish and take care of their precious things. I bought 100 obsolete costumes from the Shakespearean Festival a while back. I picked up some surplus at the Western States Belly Dance Conference. I am preserving history while saving things from the rag bag!

"I always write down all the information that is known about an item," she said, picking up a blue pioneer street dress that could be adjusted to three different sizes. "You might want to exhibit it later."

A graduate of the University of Utah in theater and dance, Maxfield had several movie and Broadway offers after her Miss USA reign. But she was asked, "What do you want to be doing in 10 years?" and decided to pass up the bright lights for making a home and family. She and her husband, Richard, an educational psychologist, have eight children and 11 grandchildren.

Maxfield is a handsome woman, with a Rubenesque figure and a face in many ways prettier than in her beauty queen days. "One of my friends says, Charlotte, you're a cross between classical and Texas dazzle," she laughed.

The clothing is a responsibility, with thousands of items - enough authentic and significant things to stock a museum - and she's thought of opening one. "This service needs to support itself," she said. "I consider my rentals a contribution toward my further acquisitions, and I did run up quite a debt in Australia and Philadelphia."

Maxfield supports her own expensive habit, paying for costumes by doing some substitute teaching, and giving workshops and classes in the general realm of personal improvement - manners, style and "becoming the woman you want to be." "I love high school kids and want people to be their best selves, forgive themselves and realize their potential," she said.

She'd like to teach a class at Cottonwood High community school, called "Make-overs," stressing physical fitness and appearance, and personal improvement. For high schools she visualizes a parade of clothing of America, or clothing of the world, or fads.

Down Under she found leather capes and boots, and enough stuff to dress a Crocodile Dundee for Halloween. She also picked up the gear for a man and girl from Snowy River, including Akubra hats made of kangaroo hide, and Drizabone (dry as a bone) drovers' coats.

"In Philadelphia I got a lot of '50s things," she said, "even some blue suede shoes, and this orange-beaded flapper dress from Paris, and apricot velvet cape with white fur." A prowl through little shops in New England yielded many finds, fresh from their original attics.

"My costumes fall into four categories: national authentic, vintage, masquerade and fads, which are a lot of fun," she explained. "I pick up screwy things at the end of seasons for a song, store them, and later they make good gags. For example, I still have original poodle skirts from the '50s."

She can also costume whole parties - perhaps in "Happy Days" style or "Mash," "Arabian Nights" or a Hawaiian Luau - at group rates, incidentally. "I'd love to do a murder party sometime, with clues dropped by the costumes," she said.

You will find gowns for prom queens, or beaded flapper shifts with feather boas, frilled bareback riders' dresses, and oceans of scarfs and gauzy drapes, shot with metallic thread, sequins and beads.

A Buddhist monk's robe, trimmed with antique braid worked in the "forbidden" stitch (so declared by a Ming dynasty emperor because it was leading to blindness in those who did it) was probably rescued from the rubble of a bombed-out monastery and ended up in a trunk in Salt Lake City.

Japanese kimonos with elaborate gold embroidery include a complete wedding outfit for bride and groom. There are colorful handwoven woolen pullover tops from the Andean Indians, a caftan from Afghanistan and boots of elaborate, bright patchwork from Nepal.

"The only other civilization that does such patchwork is the American Seminole Indians of Florida," said Maxfield, fetching a gaudy skirt with rows of symmetrical patches. "They were forbidden to use beads and leather, so they substituted this way of decorating their clothing."

In all the years of giving programs and renting out, Charlotte's only lost one thing - the evening gown in which she won the Miss USA contest. It's a white, bare-shouldered gown with a crisscross halter top, long circular skirt with strips of iridescent cloth running through, and there were matching, beaded white shoes in which she was married. Has anyone out there seen it? She may have lost it after an assembly at Weber State College in Ogden.