Donald A. Windsor
Four thistle species live in Chenango County. Ranked in order of the most common to the least, they are: Canada, Bull, Pasture, and Welted. Note that, of the four, only the Pasture Thistle is listed as native by this authoritative reference.
Mitchell, Richard S. ; Tucker, Gordon C. Revised Checklist of New York State Plants. Albany, NY: New York State Museum. 1997. 400 pages. The exact page numbers appear in  below.Canada Thistle Cirsium arvense Alien 
Bull Thistle Cirsium vulgare Alien 
Pasture Thistle Cirsium pumilum Native 
Welted Thistle Carduus crispus Alien 
We also have Sow Thistles, which are not true thistles.
Here is the Spiny-leaved Sowthistle Sonchus asper Alien