Bonnie Cashin, one of the first designers to create and popularize that uniquely American approach to dress called sportswear, died Thursday after open heart surgery at New York University Medical Center. She was 84 and lived in Manhattan.
Ms. Cashin was one of a handful of women in the 1940's and 1950's who made an important contribution to American fashion, at a time when Parisian couturiers dominated the runways and supplied most of the original fashions for manufacturers to copy. The breakthroughs achieved by Ms. Cashin and designers like Claire McCardell, Vera Maxwell, Anne Klein and Anne Fogarty still influence the way women dress, and paved the way for the success of American designers like Ralph Lauren, Donna Karan and Calvin Klein.
Renowned for her loose-fitting sportswear, Ms. Cashin described her unstudied, casual designs as ''articulating with the body.'' She was an early proponent of layering -- using several layers of light, fluid clothes, rather than one heavy garment. She pioneered the use of grommets in place of buttons and was the first important designer to make ponchos for women, introducing lightweight capes and ponchos that, she explained, ''didn't look like a horse should wear them.''
As far back as 1943, she showed boots with tweed suits and included them in almost every subsequent collection. Her ''pocketbook'' pocket, with a snap closing, was another feature that long distinguished Cashin designs. She was ahead of her time when she introduced canvas raincoats in 1952, industrial zippers in 1955, jumpsuits in 1956 and suede Indian dresses with fringes in 1957.
She opened her own business, Bonnie Cashin Designs, in 1952 and for the two ensuing decades also designed leather, jersey, canvas and tweed clothes for Philip Sills. In addition, she created handbags for Coach Leatherware, gloves for Crescendoe-Superb and rainwear for Modelia. In the early 1970's, she branched out into knitwear with styles knitted to shape, rather than cut and sewn, and with welt hems instead of traditional hems or ribbed cuffs. A popular innovation was a roomy turtleneck that did not require a zipper to get over the head.
Although her themes were often adopted by other designers, Cashin clothes had a look of their own. Her tweed ponchos were bound in leather, and her coats had a special, supple swing. For several years, there were Cashin departments in chic Paris and London stores.
''Women buy Cashin clothes because they are cozy and comfortable, not because they bowl people over,'' the fashion writer Bernadine Morris wrote in The New York Times in 1968.
Her gloves had many of the same features as her clothes. Grommets were arranged in the back of one style so that the glove could almost have served as a set of brass knuckles. Brass toggles not only were ornamental but also held a pair of gloves together or attached them to a belt. Some had drawstrings at the top that could be tightened to keep out the wind.
Her classic designs for Coach in the early 1960's were the shoulder bag and what was called the Basic, a smaller clutch style with a removable shoulder strap. The first bag she designed, a leather carryall modeled after paper shopping bags, was later discontinued but has since become ubiquitous in the collections of numerous handbag companies.
She was intolerant of anything ugly, in appearance or design. When she traveled, she draped lengths of Thai silk in her hotel rooms and ordered quantities of flowers. She was also generous on the road, dispensing items in her wardrobe to anyone who admired them. She usually returned with a different wardrobe from the one she had packed, not only because she had given away her clothing but also because she was interested in acquiring fashion ideas from other countries.
''Travel is my education,'' she said in a 1961 interview with Charlotte Curtis in The Times. ''Even if I don't use an idea right away, it's there.'' The idea of layering came from time she spent in Asia. ''The Japanese refer to cold weather as a nine-layer day,'' she explained in 1950. ''Hot is a one-layer day.''
One of her best-known innovations was the ''dog leash'' skirt, which came about because she was constantly holding her skirt going up steps in her country home in Briarcliff, N.Y. The long wool skirt could be instantly shortened by latching a small brass ring sewn near the bottom to a small brass clasp at the waistline.
Ms. Cashin was born on Sept. 28, 1915, in Oakland, Calif., the daughter of Carl Cashin, a photographer and inventor, and Eunice Cashin. The family lived in several towns in northern California during Ms. Cashin's early years, and in each her mother would open a custom dress shop. As a child she was given fabric scraps as playthings and soon began sewing and designing.
Shortly before her graduation from high school, she showed some of her sketches to the director of a Los Angeles ballet company and was hired to make costumes for the next performance. After graduation, she joined the company as its designer and in 1934 accompanied the manager to New York when he took over the Roxy Theater. Not yet 20, she created three costume changes a week for each of the variety theater's 24 dancers.