Highway 3 is a route I've driven frequently and often in my life. Traditionally I've remembered Sanford as having a neat collection of miniature elevators next to the drive-in and a well spray painted set of girders on the north side of town, all of which is gone now.
The cache is an easy drive-up find, but approach from in town instead of parking on the highway. It's findable in winter, but access may be an issue if the road isn't plowed.