I absolutely agree on the current WT rye. I had some just last night. It is one of the finest spirits in America today, at any price. It has a marked rye taste but in a subtle, even elegant interpretation, despite the 100 proof. I don't have the exact spec at hand but I think it has more than 51% rye content. Some Kentucky ryes certainly have more than 51% rye, I think Overholt has around 60%. It is true that Old Potrero is made from 100% rye, all malted I believe.
Samuel M'Harry was an early American distiller. He wrote a book in about 1810 on how whiskey was made. A reprint of the book is available for purchase at
http://www.raudins.com. In that book, he indicated whiskey was distilled from varying combinations of rye, corn and barley malt. He said all-rye could be used, or all-corn (plus barley malt for conversion of starches to fermentable sugars, i.e., his rye and corn were used unmalted ). So there was no fixed formula even in Pennsylvania where M'Harry was from. The archeological work done on the George Washington farm distillery shows that rye, corn and barley malt were brought from the farm in proportions roughly corresponding to the mash bill that Overholt is made from today. So, while some whiskey was made only from rye and malt (or maybe malted rye in some cases), much of it from the beginning was a combination of rye, corn and barley malt. Often one grain (corn or rye) was the majority grain and the others the small grains. However again some whiskey always was made from rye only plus again barley malt. The Byrn distillery book also sold at
http://www.raudins.com, chronicling whiskey production in the mid-1800's, gives a standard recipe for whiskey as 80% rye grist with the rest barley malt. But Byrn notes rye (by then, it was different earlier) was the cheapest grain and wanted to show whiskey could be made from all-rye to benefit from the greatest economy. M'Harry was concerned with economics too but also with taste, and his preferred combination was 2/3rds corn and 1/3rd rye, pretty close to the modern bourbon spec in fact. As I recall he also approved of a 50/50 combination. So while I greatly respect the Potrero initiative, I believe again it represents the way some whiskey was made in early days, not all. And even within that grain mashbill, some whiskey even in early days was aged longer than a year or two, M'Harry (and Byrn) make this clear. I believe too that even early rye whiskey made from all-rye and aged only a year or two did not, all of it, have the marked "distillery" character of Potrero. Some whiskey would have been multiple-distilled or other treated to rub out some of that taste. It is really interesting to read M'Harry writing in the very early 1800's. It shows that whiskey was not made in only one fashion, that some of it was aged, or rectified in different ways. The work done on the Washington project shows that Washington sold common whiskey as it was called for most of his production (i.e., new white spirit) but he also sold some highly refined, well-aged and/or flavoured whiskey. The common whiskey may have tasted like the Old Potrero rye whiskeys although we can't be sure of this. The aged Washington whiskeys may have tasted like Old Overholt today.
Last point: when asking about rye whiskey, we should recall the vital point that early rye whiskey and this extends into the modern era, was straight whiskey. This means it was not blended with neutral spirit, or flavored, or a high-proof spirit. Moreover, it was and is aged for a few years in wooden barrels, the best of it in new charred oak. In whatever still it was or is produced, genuine rye whiskey is distilled at under 160 proof to retain sufficient body and taste from the grain congeners that a higher disillation proof would remove. The Canadian Alberta Premium is a worthy whisky and has some straight-type whiskey blended in. But it is not a traditional rye whiskey in the American sense. Most of Alberta Premium is distilled out at over 190 proof and has when new a fairly neutral taste (though not completely neutral, and aging imparts a barrel character to it as well). In contrast, Old Potrero is and all the Kentucky ryes are genuine straight whiskeys. The Alberta Premium is a true rye whisky in the Canadian sense however, since the tradition of straight whiskey has been lost in Canada. Except for Forty Creek's whiskies from Ontario which are a kind of bridge between the two types, Alberta Premium is as good as Canada has today together with some others such as Seagram's Limited Edition (which is pretty good, I had some last night too).
Gary