Digging deeper, the Blues Festival (’largest West of the Mississippi’) runs 4 days this year with >100 performances on four stages and is expected to draw 120,000+
http://www.waterfrontbluesfest.com/history/fastfacts.html
Starting from 3PM Thursday July 3rd and ending at 1AM July 7th.
And Obama pulled more than half that total attendance in just a few hours! Yah, those estimates might be a teensy bit on the high side... ;)
So the bottom line is simply the normal size for the annual Blues festival/boat regatta w/free beer and music with some photoshopping to appear larger?