Nancy Drew looks darn good in knee socks for a 77-year-old. In fact, she looks younger now than she did when she was first introduced to America in 1930.

Sixteen-year-old teen star Emma Roberts, with long, straight, light- brown hair kept out of her eyes with headbands, a wide smile reminiscent of her Aunt Julia's and several pairs of penny loafers, is the latest embodiment of the young sleuth. She's now on the big screen in the Warner Bros. film "Nancy Drew," opening today.

But when the first Nancy Drew debuted on the book jacket of "The Secret of the Old Clock," she covered her much-blonder hair with a cloche hat, wore a sophisticated skirt suit and heels. In 1959, when that first book was updated for the next generation, Nancy's hair was more of a bouffant and her dress was a slim-cut, knee-length green sheath.

All these versions of Nancy — and lots of other Nancys in between — have a style that is best defined as classic. But finding a way to capture her look for a 2007 movie wasn't as easy as that may sound.

"Everyone has in their mind who their Nancy Drew is. She's been around so long, she's iconic," says Jeffrey Kurland, costume designer on the film. "It's an interesting problem to address the different generations. She's been around since the '30s and reprinted almost every decade, so everyone has had a slightly different picture."

Kurland says he tried to put the essence of each one of those looks into this one.

"You don't look at her and see her in period clothes, but they're not contemporary clothes. They're Nancy Drew clothes."

That means she's neat, proper — and never a fashion victim.

"I can't think of anything Nancy has worn over the years that also were absolute 'dont's' for now," Kurland says.

In fact, when the new friends she makes in the movie take her to a chic boutique for a makeover because they think Nancy's style is outdated and boring, the saleswoman compliments the young detective's rust-colored drop-waist dress with slim riding-belt details and a cropped dark green jacket. She has less kind words for the other girls.

There were 56 mysteries in the original series up through 1979. When Simon & Schuster bought the Stratemeyer Syndicate that owned the books from Grosset & Dunlap, another 119 digest-style books were published. Since then there have been spin-off series for teenagers, early readers, combined stories with the Hardy Boys and a Nancy Drew cookbook. (And even a TV series.)

Most of the original book series was written by Mildred A. Wirt Benson, the first of several generations of ghostwriters. All the books — even the most recent "Clue Crew" stories that turn Nancy into a tween — are credited to Carolyn Keene.

The same illustrator, Russell H. Tandy, did the first 26 covers, so there was a consistent look, said Siobhan Ciminera, an editor at Grosset & Dunlap, but even then her hair color drifted from blond to deep red. In the late '50s, the text began to call it "titian."

"Russell Tandy set the standard from the beginning. Everyone built their vision on that," says Jennifer Fisher, a devoted fan who created the www.NancyDrewSleuth.com Web site and plans the annual Sleuths convention, being held this year in Pasadena, Calif, to coincide with the movie's release.

There's always a nod to whatever era Nancy is currently living in, but it's subtle, especially on the cover, Fisher says. The line drawings sometimes found inside the books often were more influenced by current fashion, she adds.

Fisher loved Nancy's style in the early books, especially when she wore the cloche in "The Secret of the Old Clock" and when her hair was at its most golden on the cover of "The Secret of the Old Attic" (1944).

"What I like about the look of those covers is that they have a sophisticated elegance of the way she's depicted, not like your average 18-year-old," Fisher says.

In the new movie, Nancy wears a lot of plaid, including a drop-waist minidress that has a little bit of a '60s vibe and a cool shiny double-breasted trench coat — an item every good detective should have.