Illinois Large-Scale Topographic Quadrangles Illinois State Library

The two inventories below represent the Illinois State Library’s print collection of large-scale (1:24,000 and 1:62,500) Illinois topographic quadrangles produced by the United States Geological Survey (USGS) over the last 120 years. The first inventory names all the 7 1/2 minute quadrangles; the second names all the 15 minute quadrangles. Both are arranged alphabetically by quad name primarily, and then secondarily by date, with latest first.


Column Explanations

Minute: This column simply indicates whether the quad is an older, superceded 15 minute (1:62,500) map or the 7 1/2 (1:24,000) map.

QuadName: The list is generally alphabetically by the name of the quad as printed on the map. The name was taken exactly from the published quad, which means some quads have “Mount” abbreviated and some do not, quads which have two states listed sometimes changed the order of the two states between editions, and one word names have become two or vice versa. The state name has been omitted when it is Illinois only, but stated when it is two or more.

SortDate (and other date columns): These inventories were created using Microsoft Access. Since separate columns exist for survey, printing, edition, revision, reprint, and photoinspection dates, the creation of a "sortdate" column was necessary to produce a list in the proper order, as it could not sort through all these columns to pick out the latest date from any column. This column keeps the different editions in chronological order and is a condensed version of all the various kinds of revisions that a topo quad may have. "P" in the edition column indicates a provisional edition. "PR" in the revision column means photorevised.

QuadNumber: For 7 1/2 quads, the USGS code for the quad, based on 1-degree blocks of latitude and longitude plus an alphanumberic for each quad, is given. The State Library does not use these quad numbers for filing or retrieving, but the index map does.

Copies: In addition to the number of paper sheet map copies (blank meaning 1 copy), this column indicates, for only a few 15's, whether the quad was in microfilm only (mf), or detached from (ff) or still bound (if) in the USGS geologic folio.

In addition: The print version also contains lists of a few special types of Illinois large-scale topo quads: the 1:24,000 and 1:48,000 advance sheets, a few "[city] & vicinity" 1:24,000 quads, the 1:125,000 quads, a few DMA 1:50,000 quads, and two double 15 minute quads.

Availability: The State Library can make color to-scale photocopies upon request for a fee, but does not sell the originals. For more information, or to obtain a print version of the inventories, please call 217-782-7596 or email