Daisy is darling, Iris is sweet,
Lily is lovely, Blossom's a treat.
Of all the sweethearts a guy could meet,
well I finally chose
an American beauty rose.
- Altman, Evans, and David. Sung by Frank Sinatra.
The rose called American Beauty was bred in France by Henri Lédéchaux, and was originally named the Mme Ferdinand Jamin (M. Ferdinand Jamin was the nurseryman for the French town of Bourg-la-Reine). As a Hybrid Perpetual it blooms in early Summer and again in the Fall, always in large, repeating cupped blossoms possesing a strong traditional rose fragrance.
Not to be confused with the Miss All American Beauty Hybrid Tea Rose or the American Beauty, CL climbing rose, the true American Beauty has fallen out of favor with growers for better modern hybrid varieties. It now has an "old-fashioned" connotation among rosarians, and as a motif for quilts, china, and wallpaper, recalls the feel of the Gilded Age.
It first arrived in the US in 1875, and because it featured long stems with sparse thorns and attractive foliage (not to mention the blossom), it quickly gained a reputation as the stately queen of roses, and commanded a queenly price: once source quotes a price of two dollars per stem -- in 1886, no less. It is to this day the official flower of Washington, D.C..
Since the selection of popular music which accompanied the film American Beauty did not include any Grateful Dead (although Sugar Magnolia would've been a great addition to the soundtrack, IMHO), and roses were central to much of its plot, I propose that it is this variety of rose which lent its name to the 1999 film, as well as two before that in 1916 and 1927 (see http://us.imdb.com/Title?0006358 and http://us.imdb.com/Title?0017626). It should be noted that neither the roses that Carolyn Burnham is seen growing nor the petals that covered Angela Hayes's naughty bits are actually American Beauties.
Sources:
http://www.chambleeroses.com/americanbeauty.htm
http://www.uncommongarden.com/r/americanbeauty.html
http://www.helpmefind.com/sites/rrr/pl.php?n=192