You got me curious about that comparison. Of course we all know about Xenia's F 5. Greene County, OH is 415 Square miles and Van Wert County is 410 square miles, so they are comparable in size.
According to the Tornado History Project stats, Van Wert County experienced 33 tornadoes from 1/1/1950-8/24/2016, while Greene County had 17 tornadoes from 2/25/1956-5/26/2015. So Van Wert Co. has averaged exactly 1 tornado every 2 years, while Greene Co. has averaged 1 tornado every 3.48 years. I will have to check the other counties in this part of the subforum when I have more time, but 1 every 2 years in a county of that size, especially in this part of the country, seems fairly impressive to me.