Dating H.M.Gousha Gas Station Road Maps including Map Codes

Map Codes

It is important to understand "Map codes" to be able to quickly date maps published by H. M. Gousha.  Map codes are in very small numbers and letters and are  located on the bottom line of each map.  There can be different map codes on each sub-map that is part of the overall map.  For this discussion I am going to refer to  the map code on the large state map on any given state map.  I think the best example of a map series using the Gousha map codes is the CONOCO Colorado map series.  CONOCO used Gousha maps continuously from 1927 to 1981, so by looking at the Conoco-CO-Spreadsheet page you can see the complete Gousha map code sequence for CONOCO Colorado maps.

Letter Codes

Gousha map codes start in 1927 and include the letter "A" and continue with a single letter each year until 1952 with the letter "Z"  then they start over using double letters in 1953 with the letters "AA" and continue using double letters until 1978 with the letters "ZZ", from that point on they get a little confusing and I will not discuss that here.

               A  1927                   N  1940                  AA  1953                   NN  1966

               B  1928                   O  1941                  BB  1954                   OO  1967

               C  1929                   P  1942                  CC  1955                   PP  1968

               D  1930                   Q  1943                  DD 1956                    QQ  1969

               E  1931                   R  1944                   EE  1957                   RR   1970

               F  1932                   S  1945                   FF  1958                    SS   1971

               G  1933                   T  1946                   GG 1959                    TT    1972

               H  1934                   U  1947                   HH 1960                    UU   1973

               I   1935                    V  1948                    I I   1961                    VV   1974

               J   1936                  W 1949                    JJ  1962                    WW  1975

               K  1937                   X  1950                   KK 1963                    XX   1976

               L   1938                   Y  1951                   LL  1964                    YY    1977

               M 1939                    Z  1952                   MM 1965                   ZZ    1978

Map Base Codes

As part of the "Map Code" you will see a three digit number that changes every few years, this is the map base code, I assume it was revised each time they made a major revision to the map format, you will see the Colorado map base codes are as follows:

141   from 1928 to 1930

241   from 1931 to 1935

341   from 1936 to 1940

347   from 1941 to 1946

519   from 1947 to 1966

601   from 1967 to 1981

Other state maps have different map base codes but follow a similar pattern.

J or JC

Many of the Gousha "Map Codes" include the letter J or JC.   I don't know the meaning of these letters, but they can sometimes confuse dating maps by map code.  They don't seem to have any value in dating Gousha maps.

Month Code

Many map codes contain a number between 1 and 12, this appears to be a month code and will vary in location in the codes.

Small Date Codes

"Small Date Codes" are separate from the "Map codes" and in the case of Conoco maps are found on the back cover in the lower right hand corner from 1938 to 1963.  They usually contain 4 numbers like 4382, the 4 is the month of issue, the 38 is the last two digits of the year of issue, and the 2 is the revision number.  These codes are excellent for quickly dating maps as you do not have to open the map to read the code and for the most part these codes are unique to a given map, but they may not be consistent with the "Map codes" when dating maps.

Other dates

There are other dates on the maps as you will see on the Conoco-CO-spreadsheet including Census dates, Edition dates and copyright dates.  You will notice that these dates are often inconsistent with each other and the map codes resulting in inconsistent dating when you are shopping for maps.

               Edition Dates are usually consistent with map codes

               Copyright dates are fairly consistent

               Census dates are the least accurate way of dating maps

If you are a map seller, I recommend that you include both the "Map Code" and the "Small Map Code" in the auction, so that any knowledgeable collector will know exactly what you have.  If you just state a date for a map, the potential buyer does not know how you dated the map.

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