Where in the United States is there the highest ratio of women(in
their forties)to men?

I haven't been able to find information that limits the findings to
people in their forties, but this article provides some information
that you might find useful:

"Listen up, bachelors: The highest concentration of single women is
generally in the South and East. Alabama and Maryland, for example,
had 79 single men for every 100 single women. Among metropolitan
areas, the most guy-friendly ratios were in Roanoke, Va., and
Sarasota-Bradenton, Fla."

http://www.reviewjournal.com/lvrj_home/2003/Oct-27-Mon-2003/news/22445196.html

This may also be of interest:

"According to the Census Bureau, the highest ratio of men to women is
Anchorage, AK, and women to men is in the Sarasota-Bradenton, FL,
area."

http://www.findarticles.com/cf_dls/m0BQK/3_6/74699554/p3/article.jhtml?term=

Figures from the US Census on unmarried women and unmarried men:

http://www.census.gov/population/cen2000/phc-t27/tab05.pdf