The four trails covered here - 400 State Trail, Elroy-Sparta, La Crosse River, and Great River Trail - are almost entirely crushed limestone surfaces.
This type of surface is a very small gravel that packs down pretty hard, although it may be soft after a strong rain.
A few short sections are paved. On the Elroy-Sparta Elevation Charts
the paved portions appear in the charts as solid
color. The striped parts, which make up the vast majority of the trail, are crushed limestone.