The San Marzano is considered to be the best flavored tomato for whole canning and sauce making (Just for the record, I personally dispute this - ask me why when you see me next). 
 
Plants are large and of good disease resistance. Vibrant red fruits are plum-shaped averaging 4-6 ounces, with thin skin and very meaty flesh. Whole fruits peel easily and cook down quickly, which is a nice bonus to their sutble sweet flavor.

HISTORY: Improved Italian heirloom. The San Marzano II strain originates from Parma, Italy, where it was developed for the 1950's canning industry.