The water main broke just after midnight Thursday at the intersection of South Main and Green Street in downtown Rockford.
The 300 block of south main has been without water all day while more than a third of the city has been under a boil order advisory.
Most of the time a water main break doesn't cause a lot of problems, but the water main at South Main and Green is one of the largest in the city - a 16 inch pipe - that literally blew up the road and sent water rushing into the nearby Rock River.
On The Waterfront will continue as planned, but businesses in the 300 block of North Main shut down for the day; water was totally cut off to them, and 39 schools also took a hit.
At King School, bottles of water had to be brought in for students and distributed throughout the day.
The On the Waterfront kick off concert featuring Styx is still on schedule, however; much work was done through the day on the Great Lawn in Davis Park.
It was hit with water runoff from the main break and partially flooded.