Unless some great improvement has taken place in the last few years then this is a bit of an exaggeration:

(from here [1])

Since 1987, Boomsday has been a successful one-day free event that has brought hundreds of thousands of people to Knoxville’s Volunteer Landing and Neyland Drive for what has become known as the nation’s largest Labor Day weekend fireworks show.

Emphasis mine.

I haven't been in years to either one, but Cincinnati's Labor Day fireworks display makes Boomsday look quaint by comparison.