You are probably waiting on this impatiently too. The video on how to prepare for this
event and be able to search the free pages, says we should get the enumeration district by
visiting this page
http://www.archives.gov/research/search/
and doing a search for
"1940 Census Maps County State"
I took the liberty to do Miami CO, Indiana and here is the direct link to the maps.
Have fun!
http://research.archives.gov/search?expression=1940+Census+maps+miami+ind...
for more topics, look at
http://www.archives.gov/research/census/1940/
for the video:
http://1940census.archives.gov/
Regine Brindle