I can give you anecdotal stuff and some stuff to boost your odds, from someone who's been in the online tickling community for over 25 years, based on chat rooms, personal ads and other TMF member profiles, and other online and offline contacts with others in the community:
States that have shown up the most, under the criteria above, have been Michigan, Ohio, Texas, and New York (the city and upstate). Just keep in mind that people move a lot, and these states are based on decades of contacts here and there.
A basic rule of thumb to follow is population density. When Craigslist had personal ads, the most frequent tickling personals were in highly dense areas----New York City, the big cities in Texas, Chicago, etc. Your odds are better there, or as someone mentioned, a city like Philadelphia because not only is it dense, but it has inflows of people from other nearby dense areas, like NYC, NJ, etc., thanks to commuter trains. Good luck.