I am a Girl Scout Leader, trying to impress on my Senior Scouts how
elite they are. I am looking to find how many 17-18 year old girls
there are in the
US.  I would also like to know how many are in NJ if possible.  Only
1.5 percent of girls that age in the US are Girl Scouts, and only
3,500 of those receive the Girl Scout Gold Award each year.  I'd like
to be able to tell them how many girls are eligible to be Senior
Scouts and receive the Award.

According to estimates based on the 2000 US Census, there are 101,410
females aged 17 or 18 in the state of NJ, and 3,927,477 in the US. 
Your 3,500 girls, therefore, represent 0.09% of 17-18 year old girls
in the US.



NJ Data:
http://factfinder.census.gov/servlet/DTTable?_bm=y&-context=dt&-ds_name=DEC_2000_SF1_U&-CONTEXT=dt&-mt_name=DEC_2000_SF1_U_PCT012&-tree_id=4001&-redoLog=false&-all_geo_types=N&-geo_id=04000US34&-format=&-_lang=en

US Data:
http://factfinder.census.gov/servlet/DTTable?_bm=y&-context=dt&-ds_name=DEC_2000_SF1_U&-CONTEXT=dt&-mt_name=DEC_2000_SF1_U_PCT012&-tree_id=4001&-redoLog=false&-all_geo_types=N&-geo_id=01000US&-format=&-_lang=en

Thanks for such a quick and precise answer!!!!!   It's exactly what I needed!