Oleg Cassini (1913 to 2006)

Then: Debonair Oleg Cassini had a thriving career in film costumes, but his creations reached their widest audience when Jacqueline Kennedy chose him to mastermind her White House wardrobe. The French-born émigré shunned elaborate designs for sleek, tailored shapes — A-line sheaths, boxy jackets — that didn’t distract from the woman who wore them. “Cassini’s style was structured and tasteful,” says Pamella Roland, a designer based in New York City. This classic simplicity made Cassini a star — and Jackie Kennedy a paradigm of chic.

Now: A sleeveless sheath dress epitomizes Cassini at his minimalist best. Belted or skimming the waist, the straightforward shape works on all body types. Top it with a boxy jacket with lady-like three-quarter-length sleeves when you want a more pulled-together look.