I haven't read any of the other replies so I apologize if this has already been posted. They're what the budding custom shop known as Deflave Precision uses. At least that's what came on the one build of his that I could afford...
Expand the Montana layer as shown in the first pic below. Then click on the polygon you want to turn off, also shown in the first pic. That'll highlight it in the Montana layer. Uncheck that particular highlighted polygon.
P.S. PM me your email address and I'll send you something that may...
Click on "Adjust Opacity," which is next to the magnifying glass on the left side. Move slider to desired transparency.
It appears the data for MT is not all that current.