Most USGS topographic maps use contours to show the shape and elevation of the terain. Elevations are usually shown in feet, but on some maps they are in meters.
Contour intervals vary, depending mainly on the scale of the map and the type of terrain.
Such detail is useful for engineering, local are planning. They cover large areas and are used in land management and planning. Indexes are available for all series. The maps use National Geodetic survey horizontal and vertical datums and State and UTM coordinate reference systems.