"The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth's surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level. Contours make it possible to show the height and shape of mountains, the depths of the ocean bottom, and the steepness of slopes."

Source:  What is a topographic map? USGS FAQ

Map Scale

Simply defined, scale is the relationship between distance on the map and distance on the ground. A map scale might be given in a drawing (a graphic scale), but it usually is given as a fraction or a ratio-1/10,000 or 1:10,000. 

1:10,000 is a larger fraction than 1:250,000, therefore 1:10:000 is a large-scale map, showing a smaller geographic area in greater detail while a map at 1:250,000 is a small-scale map showing more geographic area with less detail.  Digital maps that have implemented scale dependent display features allow you to intuitively engage the different map scales when you see more details as you zoom in to the map image.

Topographic maps are produced at both large- and small-scale and the NU Libraries Map Collection includes topographic maps at various scales for the United States and other countries around the world.

An example:  snip from the Mt St Helens, WA 2020 map at 1:24,000 (click image to see full extent of this map sheet)

NU Libraries Map Collection Topographic Maps

The Northwestern University Libraries Map Collection has topographic maps for the U.S. and other world regiona.  The U.S. maps were produced by the U.S. Geological Survey (USGS) in multiple scales.  Our collection includes:

1:24,000 scale for the following Midwestern states:

    Illinois
    Indiana
    Iowa
    Kentucky
    Michigan
    Minnesota
    Nebraska
    North Dakota
    Ohio
    South Dakota
    Wisconsin
    Puerto Rico / Pacific Islands / Territories

At smaller scales including 1:31,680, 1:62,500,  1:100,000 and 1:250,000 are maps for the entire U.S.

US Topographic Maps Online

The USGS topographic maps are available for downloading from the following selected websites:

USGS TopoView
Topographic maps created by the USGS 1879-present.  The same area may be mapped at different scale and at different times allowing study of change of natural and human-made features.  Maps available in GeoTIFF, JPG, KMZ formats.

USGS Map Locator & Downloader
USGS's official topographic maps (7.5'=1:24K, 30'x60'=1:100K, 1=1:250K) download site. Maps are in the GeoPDF format.

Libre Map Project
The Libre Map Project houses map image files (TIFF), GIS Data and documentation. Its data includes 24k scale USGS DRG data, SVG coundary files, TIGER/Line data and GeoNames. Users can search by state, place name, and feature, and data is available in tiff, tfw, fgd, and TIGER/Line formats.

Historical Topographic Maps
The followings are selected sites which offer historic topo maps.

USGS Historical Topographic Maps in TopoView provides GeoPDF format

University of Illinois Urbana Champaign Historic Maps Digital Collection
Includes historic topo maps of Illinois of various scales.

Broer Map Library
Check sections with names like "[State Abbreviation] USGS Maps"

To identify what topographic maps may be available in the Northwestern University Libraries Map Collection for a country or region of interest to you, please make an appointment by contacting govinfo@northwestern.edu .  Our collection is globally representative.

Online Topographic Maps

Most topographic maps of the world are available for sale only. Exceptions are worldwide topographic map series by US mapping agencies (some are restricted). To find world topo maps, try the following:

Perry-Castañeda Library Map Collection - Topographic Maps
The University of Texas Libraries scanned print maps and made them available on the web.  This site is archived as of 2021 and no longer being updated.