By Harrison Jacobs From Business Insider

Roger Marshutz/Courtesy of Estee Stanley

“The King” Elvis Presley is regarded as one of the most significant culture icons of the 20th century. To this day, he is the best-selling solo artist in the history of recorded music.

What exactly do we mean when we call someone “cool?” Most would struggle to describe it, but just about everyone knows “cool” when they see it. It is a distinctly American invention that finds its roots in African-American culture, Jazz, and the multitude of icons that the American fame machine has produced.

A new exhibition and book, “American Cool,” currently on display at the National Portrait Gallery in Washington D.C., traces the origins of “cool.” It also includes a look at the 100 “coolest” Americans of all time.

To decide who made the list, curators Frank H. Goodyear III, the co-director of the Bowndown College Museum of Art, and Joel Dinerstein, the director of the American Studies program at Tulane University, engaged in a vigorous debate based on four criteria.

Dinerstein explained to PBS Newshour: “First an originality of artistic vision as established through a signature style, which is to say their artistic vision cannot be separate from their personality. Second, that in a given historical moment, they were perceived as a cultural rebel. Third, that they have high profile recognition. Fourth, that they have a recognized cultural legacy.”

While the usual suspects are featured, including James Dean, Jimi Hendrix, and Hunter S. Thompson, there are many less obvious faces on the “cool” list as well. All are, however, what Dinerstein calls, “the successful rebels of American culture.”

The National Portrait Gallery shared a selection of the portraits with us here, but you can see the entire collection in the book or at the gallery until September 7th.

Long Island-native Walt Whitman was a poet, essayist, and journalist, best known for his seminal poetry collection “Leaves of Grass” (1855), which was criticized for its overt sexuality.

Samuel Hollyer/Smithsonian’s National Portrait Gallery

Walt Whitman

Frederick Douglass was an African-American orator, writer, statesman, and activist. After escaping from slavery in 1838, Douglass wrote a landmark autobiography of his experience and became a leader of the abolitionist movement.

National Portrait Gallery, Smithsonian Institution;

Frederick Douglass, 1856.

Leon “Bix” Beiderbecke was one of the most influential jazz soloists of the 1920s. At the time of his death from alcoholism at 28, Beiderbecke was little known outside of the jazz community.

Institute of Jazz Studies at Rutgers University

Bix Beiderbecke, 1920.

Nicknamed “the Empress of the Blues,” Bessie Smith was the most popular female blues singer of the 1920s and 1930s. She is often considered the greatest singer of the era.

Carl Van Vechten Trust/Smithsonian’s National Portrait Gallery

Bessie Smith, 1936.

Billie Holiday was a jazz singer and songwriter, whose style was inspired by jazz instrumentalists. She worked with many of the titans of early jazz, including Count Basie, Artie Shaw, and Louis Armstrong.

Bob Willoughby

Billie Holiday, 1951.

Though born in Britain, Audrey Hepburn made her mark on American culture as a film, TV, and Broadway icon during Hollywood’s “Golden Age,” with the films “Breakfast At Tiffany’s” (1961) and “My Fair Lady” (1964).

Philippe Halsman Archive

Audrey Hepburn, 1955.

Hailing from Hoboken, New Jersey, Frank Sinatra was one of the most influential and best-selling entertainers of all time.

Herman Leonard Photography LLC

Frank Sinatra, 1956.

Humphrey Bogart was named in 1999 by the American Film Institute as the greatest male star in the history of film. He appeared in such iconic movies as “Casablanca” (1942), “The Big Sleep” (1946), “The Maltese Falcon” (1941), and “Sabrina” (1954)

© Philippe Halsman Archive

Humphrey Bogart, 1944

Lauren Bacall is a film and stage actress most famous during Hollywood’s “Golden Age.” She often appeared alongside Humphrey Bogart and was a mainstay in the film noir genre, often playing the “femme fatale” role.

Alfred Eisenstaedt. Courtesy of the Time Life Collection.

Lauren Bacall, 1949.

Considered by many to be the greatest actor of all time, Marlon Brando achieved acclaim for playing the role of Stanley Kowalski in the play “A Streetcar Named Desire” (1951) and later for his roles in “On The Waterfront” (1954), “The Godfather” (1972), and “Apocalypse Now” (1979).

Philippe Halsman Archive

Marlon Brando, 1950.

James Dean is best known as an icon of teen disillusionment, which he exhibited prominently in the film “Rebel Without A Cause” (1955). He died in a car accident at 24.

Roy Schatt

James Dean, 1954.

Mississippi-born Muddy Waters is considered the “father of modern Chicago blues” and is credited with influencing some of the biggest acts of the 1960s and 1970s, including The Rolling Stones, Eric Clapton, AC/DC, and Led Zeppelin.

Charles H. Stewart/National Portrait Gallery

Muddy Waters, 1960.

Miles Davis was a jazz trumpeter, bandleader, and composer. Davis revolutionized jazz in the ’50s, ’60s, and ’70s, pioneering the jazz fusion, jazz-rock, and jazz-funk genres.

© Aram Avakian

Miles Davis, 1955.

For more on this story and to see the rest of the ‘cool’ list go to: http://www.businessinsider.com/photos-from-the-national-portrait-gallerys-exhibition-american-cool-2014-5#ixzz31q9qCfdz