I'll have to look through my collection to see which ones are blended and which aren't. I know I have a few Concannon Cabs that are 100%. Some others are Staglin and Silverado.
There are numerous blends still called Cabs but I am finding more and more 100% Cabs than in years prior. It seemed in the 80's and prior blending with just a bit of Merlot was common. I don't see that as much. Some wineries that blend with several varietals don't call it a Cab or they call it a Cab Assemblage etc.
I really don't drink a lot of Cabs lately. I do like them but its more difficult to find a great one at a great price. Their popularity grew strongly over the past several decades. One of my favorites in the 80's was Caymus SS. I bought it every year for about $25. It's now over $100 at last look.