Hawkweeds are difficult to sort out for identification. I am at least 90% sure that this one is Field Hawkweed (Hieracium caespitosum ssp. caespitosum).
Part of what makes hawkweeds difficult is the number of common names. This plant is also called Yellow Hawkweed and King Devil. The same names also apply, at times to other species of hawkweed. Not only that, the Latin has changed too. This plant is called Hieracium pratense in the Newcomb Wildflower Guide and in the Peterson Field Guide to Wildflowers; however, the Ontario Plant List calles it (Hieracium caespitosum ssp. caespitosum).
Be that as it may, the leaf having hairs on both upper and lower surfaces is what makes the identification posible. The number and size of flower heads, the colour of the stem, and the sizes of the bracts and leaves also point to the same species.
Isn't flower identification fun at times?