Kate Spade, the handbag designer turned lifestyle-brand maven, was found dead in her New York apartment Tuesday morning of an apparent suicide.

It was Ms. Spade who paved the way for a slew of women's lifestyle brands that seized our fashion consciousness back in the late 1990s and early aughts. Her signature style — work-appropriate with a definite element of whimsy — allowed for other brands launched by American women like the Main Line's Tory Burch, Michelle Smith, Rebecca Minkoff, and Trina Turk to also market themselves as lifestyle brands. On the flip side, it was Ms. Spade who also forced established brands like Banana Republic and J.Crew to make modern-meets-preppy chic.

The news Tuesday morning was shocking, not only because Ms. Spade was only 55, a wife, and the mother of a teenager, but because her eponymous lifestyle brand had such an upbeat, joyful air. This successful fashion designer was a household name, so surely, she had to be living the good life.

Ms. Spade's body was found by a housekeeper not long after 10 a.m., police said at an afternoon news conference. Her husband and business partner, Andy Spade, was in the apartment at the time. Law enforcement officials said that she left a note at the scene and they told the Associated Press that, among other things, it contained a message to the couple's 13-year-old daughter, telling her it was not her fault.

"We are all devastated by today's tragedy," her family said in a statement through a spokesman. "We loved Kate dearly and will miss her terribly. We would ask that our privacy be respected as we grieve during this very difficult time."

Ms. Spade, once the accessories editor at Mademoiselle magazine, introduced her line of colorful nylon handbags back in 1993 because, as she told the New York Times, she was over the overly adorned designer bags of the previous decade. Within a few years the Kate Spade bag — a combination of her first name and her soon-to-be husband's last name  — became as popular as Hermes, Coach (who later purchased her company), and Fendi. But the price points were hundreds of dollars cheaper than, say, a Louis Vuitton.  So they were well within the budgets of the young, strong, fashion-savvy, upwardly mobile women she marketed to.

"I remember going to the King of Prussia Mall and seeing a pink Kate Spade in shantung silk, a triangle tote bag that I just had to have," remembered Karen Giberson, president of the Accessories Council.  "And I could get it. I gave up my lunch for I don't know how many weeks, but I got it."

In 1999, the nonprofit named Ms. Spade the Best Accessories Designer.

Beth Buccini, owner of the very trendy Bryn Mawr women's specialty boutique Kirna Zabête, has similar Kate Spade memories.

"I remember when I was an intern at Mirabella magazine, and a  young, hot accessories editor-turned-designer came to visit us and brought all of her really colorful bags," Buccini recalled. "We hadn't seen anything like that before and she was letting us buy the bags wholesale. It was my first New York City fashion purchase."

Within a few years Ms. Spade expanded her empire from accessories to clothing, and her Kate Spade women's wear line would become popular with young women, teens, and their moms and grandmothers, too. The Kate Spade look was preppy like Lilly Pulitzer, but it was sleeker —  think timeless rather than retro. She managed to find the sweet spot between happy and high fashion. And she became known for the specificity of her prints. Geometric blocks were clean and square, and all of her polka dots were the perfect size.

"I remember she was all about the bow, and that made us all about the bow," said Maria Delaney, owner of Louella in Wayne, Malvern, and Bryn Mawr.

Everything about Kate Spade was buttoned up, but because of its bold color palette, that was fresh and modern. For example, it was Kate Spade who ultimately inspired me to pair kelly green and navy blue.

"It was just so tasteful," said Maureen Doron, owner of Skirt in Center City and Ardmore. Doron never carried Kate Spade, but her wedding china is, well, Kate Spade. "Everything of hers had an heirloom quality and when you put it on, you felt like old money."

Kate Spade was born Katherine Brosnahan in 1962 and grew up in Kansas City, Mo.

Within the year of her meteoric handbag launch, she created Kate Spade New York with her husband and expanded into menswear, shoes, luggage, and other accessories as well as a line of home goods and stationery. She also wrote three design books, that you can regularly on the glass coffee tables of some of America's toniest boutiques. In addition to her Accessories Council Award,  she won multiple accolades from the Council of Fashion Designers of America and was once named "giant of design" by House Beautiful.

"She was just ahead of her time," said Sheila Connelly, director of the fashion design program at Jefferson University. "One of the most important things for a designer is to have a clear, well-defined, and unique perspective, and she had that to such a beautiful extent."

Ms. Spade walked away from the company in 2007, a year after it was acquired from the Neiman Marcus Group for $125 million by the company then known as Liz Claiborne Inc. Coach, now known as Tapestry, bought the Kate Spade brand last year for $2.4 billion, seeking to broaden its appeal.

Meanwhile, Ms. Spade and her husband started a new handbag company a few years ago, Frances Valentine. And she changed her name to Katherine Noel Frances Valentine Brosnahan Spade, she said in an NPR interview this year.

"In an era when fashion designers were becoming celebrities, she helped put fashion on the map, becoming a household name in the process," said Sarah Rodowicz, the director of the Philadelphia chapter of Fashion Group International. "She was one of the pioneers behind creating an aspirational lifestyle brand."

Rodowicz went on: "That's why it's so surprising and shocking about what happened. That's why it's so important to be kind, because you never know what's going on in people's lives."

This article contains information from the Associated Press.