If it were me, I would go with either the Hartington or Winnebago towers... Just pull up the Nebraska State Patrol page and you should be able to find the info you need. Don't be discouraged if you don't hear much traffic from either tower, as it is entirely possible that the S. Sioux City area may have switched to the N-WIN system. I hear traffic occasionally from that area, but I don't hear much (I suppose it helps that I live in Norfolk.)
As of today, the NSP is still on the low-band frequencies. The Winnebago tower is the best to listen to here in South Sioux City.
I have been scanning the Fed. freqs, but still have not heard Jones Creek come live yet.
42.48000 KAB310 B 065 DPL WnnbgTwr B Base - Winnebago Tower FM Law Dispatch
42.28000 KA6007 M 065 DPL WnnbgTwr M Mobiles - Winnebago Tower FM Law Dispatch
452.25000 KAB310 F 167.9 PL Base Link to Winnebago Tower FM Other
457.25000 KAB310 F 167.9 PL Mobile Relay Winnebago Tower FM Other
There also is some activity on the AIR freq. The Troopers use that to chat car to car.
42.04000 KA6007 M Enforce 1 - Aircraft FM Law Talk
Hope that helps, but like the other posts state, check the new N-Win freqs this week, maybe they will come live. I will program them into my feed as soon as they do as well.