I would suggest doing this by percentage of population. Connecticut, for example, has entire CDPs that are majority/plurality Jewish, while in Texas, it's only about .5% of the population.
Try this list: http://www.jewishvirtuallibrary.org/jsource/US-Israel/usjewpop.html
The answers by percentage would be New York (8.4%), New Jersey (5.5%), Massachusetts (4.3%), Maryland (4.2%), Florida (3.7%), California (3.3%), Connecticut (3.2%), Nevada (2.9%), Pennsylvania (2.3%), and Illinois (2.2%), with D.C. (5.1%) as a bonus. |
State by Largest County 
Union Cities (1860) 
U.S. Largest Cities (1910)
