steve from saint louis on 8/6/2017 8:41:53 PM:
Valentine has a dedicated parking lot for bike riders on the trail that is usually vacant. Norfolk has the Ta-Ha-Zouka Park at the trailhead, which I would think would be better for long term parking. However, it is generally an uphill ride from Norfolk to Valentine. I also seen the Valentine streets severely flooded during a downpour when I was there, which might be a concern.
Nevertheless, nobody is going to guard your car while you are on the trail. If you insist on leaving a car in Valentine then it is probably best to talk to the police dept. there. They also have a nice city park there, which is easily reached from the trail if you can handle one steep hill.