The Cascade:

The Cascade, released in 1972 was one of the first commercially accepted American bred aroma hop.  This variety is a cross between a male Fuggle plant and Serebrianka (Russian hop).  The Cascade still remains the most popular hop variety in the brewing industry. 

Common Beer Styles:  Pale Ales, IPA's, and Porters
Aroma:  Delightful, Spicy, Flowery, Citrus
Common Use:  Dry-Hopping
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The Centennial:

The Centennial, also known as the "Super Cascade", was released to the public in 1990.  The Centennial is a cross between Brewer's Gold, Fuggle, Kent Golding and Bavarian. 

Common Beer Styles:  Pale Ale, American/English Ale and US Wheat
Aroma:  Pungent, floral and citrus flavors
Common Use:  Dual Purpose
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The Liberty:

Of the four triploid Hallertau varieties the Liberty was released in the US in 1991. The Liberty most closely resembles the Hallertau cultivar. The cones are smaller but dense.  They have good pickability, drying and baling characteristics.  The lupulin is a dark yellow color with moderate amounts.  This Liberty is an aroma variety that is similar to imported German aroma varieties. 

Alpha Acids:  3.0-5.0 % acids remaining
Aroma:  Mild, slightly spicy
Beer Styles:  Lager, Pilsner, Bock, US Wheat, Kolsch
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The Willamette:

Released in 1976, the Willamette descended from a seedling of the English Fuggle variety.  It is currently the most widely grown hop in the US.  Even though it has a vigorous growth habit it can still be a very manageable hop variety.  The round cone structure is small to medium size and has a fairly pale completion.  The Willamette is a good variety for pickability, drying and baling.  It also has a moderate amount of lupulin that is golden yellow in color.  A quality aroma hop is the general perception of the Willamette.