Prior to Prohibition there was a thriving brewing industry throughout the United States. The needs of the brewers, both large and small, created a substantial flow of malted barley from the grain maltsters.
During the same period in history the distillers, in additional to Rye and Bourbon, also produced malt whisky, sometimes labeled pure malt whisky. I've forgotten the distinction as to whether pure malt meant 100% malted barley or if it also applied to a mixture of malted and unmalted but the grain was barley none the less and it was unpeated.
Scots whisky as we know it today didn't come into prominence until later in the 19th century so the American malt whiskys were not simply Scottish influenced copies but their own thing run off column stills. Certainly not a widely popular style yet it was a presence on the American whisky scene.
When the question was posed earlier today over what mashbill we would like to see made pure malt occurred to me. I have purchased malts made by micros but they are not the same thing as they trace their roots to Scotland rather than American distilling tradition.