Simply stated, those launchers/missiles are kept very near surveyed launch locations with roads engineered to accommodate their limitations. Easily located by multiple eyes in the sky for targeting.
I was in a Pershing missile battalion in Germany in the early 1970’s. We generally did field training at a limited number of sites, but could be ordered to unfamiliar sites. Surveyed sites were described on two sheets of paper. One sheet was map and plot plan of the site, the other was a pen and ink sketch of local landmarks. The book containing the sites was over a foot thick, loose leaf bound, and constantly updated. There must have been over a thousand sites.
It was classified TOP SECRET. It was not just for Pershing, these were field artillery surveys.