In the year 2010, Toledo, OH (a somewhat small city) was estimated to be the per capita worst city in the United States when it comes to human trafficking; with just Miami, Portland, and Las Vegas having higher incidents per year of arrests for traffickers, and rescues of trafficking victims.
The reason for Toledo, OH being the epicenter of human trafficking is most likely due to the positioning of Ohio among the interstate routes and its place next to the Canadian border. Traffickers have underground slave auctions in and around Toledo, where other predators go in order to find victims.
Has anything changed?
During 2017, in Toledo, there have been over 200 cases of possible human trafficking (the highest number of cases yet: about a fifty-percent jump from the prior year), yet, the number of arrests for human trafficking, around seventy, is one of the lowest recorded in a given year for Toledo’s investigators.
It is speculated that the heroin epidemic in the United States (which hits Ohio particularly hard) may be something that the pimps are taking advantage of, by getting and keeping their victims addicted, the human trafficking trade has gotten worse, and it is harder for investigators to get the victims to cooperate (because the pimps are the heroin suppliers which the addicted victims turn to for more).
Like everywhere else, the overwhelming majority of human trafficking cases in Toledo, OH are unknown to investigators.
Sources:
http://www.toledoblade.com/Editorials/2018/02/09/Facing-up-to-trafficking.html
http://www.13abc.com/content/news/Ohio-investigating-more-human-trafficking-cases-472624493.html