Longest route within one specific county in your own state

[Pete from Boston]

For Interstates in Mass., without opening up any GIS program (and mostly ballparking form Wikipedia exit lists), I'm guessing it's the Mass Pike (I-90) in Hampden County at around 30 miles.  95 in Essex is probably a close competitor, and 195 in Bristol and the cumulative bits of 495 in Worcester and/or Middlesex are not far behind. 

[doorknob60]

Here's Oregon. My only methodology was guess and check though, might have missed something. I'm surprised how close these numbers are to each other (I left the top few because of how close they are).

OR-126 spends 125 miles in Lane County
OR-138 spends 124 miles in Douglas County
US-95 spends 121 miles in Oregon, all of that in Malheur County
US-97 spends 119 miles in Klamath County, OR

For interstates, I think the winner is I-5 in Douglas County at 95 miles.

[mjb2002]

South Carolina 34 is 34 miles in Newberry County. I know that US 21 is 33 miles non-concurrent to US 17 Alternate in Colleton County, but I don't have the exact mileage after that.