In 1940 Parker Bothers opened a new office in Chicago and it replaced London on the boxes and on the rules. Four common sets were still being made in 1940; the blue #6, the black #6, the green #8, and the white #9. Each of these sets still had its own set of rules. The blue #6 has squares, the black #6 has circles (this set went to wooden tokens and square rules during the war), the green #8 is still diamonds, and the #9 still has stars (the diamonds and the stars are now filled in). The short game rules now show 6 editions available; both #6s, #8, #9, #12 Library Edition, and #25 De Luxe Edition. The De Luxe Edition is priced at $35.00 on this sheet.
The changes in these rules begin on page 2."SALARY" is replaced with "SALARY (THE "GO" SPACE)". On page three "THE BANK" section has largely been rewritten, and on page four the "MORTGAGES" section has the line "No Rental can be collected on Mortgaged property." changed to "No Rental can be collected on Mortgaged lots or utilities but rent can be collected on unmortgaged property in that same group.". The blurb about extra money has also been rewritten.
In 1941 patent 1,509,312 expired and was removed from all Monopoly packaging and rules. Other than this the only other change on the rules is the section at the bottom of page four which shows other games available from Parker Brothers. These rules were used through 1946.
There are two different short game rules sheets from this time period. The first, I believe, is from 1941. This set shows the editions available as the Junior edition #6 in blue or black, the Popular edition #8 in green (which I have never seen), the White Box #9, the Library edition #11, and the De Luxe edition #12. The second, which I believe was used from 1942-1946 shows only the #6 (both blue and black), the #8 (which I also have never seen), and the #9. The more expensive editions were probably dropped due to the war. The picture of the tokens has also been removed. The short rules themselves were unchanged.
1947 saw the next change in the rules. The blue #6 gained a token and a new set of rules with triangles at the top and now had "For Three to Eight Players" under the word "RULES" on page one. The black #6 regained metal tokens and went back to circles, the #8 diamonds, and the #9 stars. Other than the change to the blue #6 rules these are identical to the 1941 rules.
The short game rules were changed completly. It was now a four page booklet with only one set of rules. The new rules are a combination of the two old short rules with a new three houses then hotels rule.