Police estimated that more than 2,000 people had gathered in the 500 block of State Street by 11:30 p.m.
The crowd continued to swell well beyond that number with singing and chanting revelers.
The Madison Police Department began dispatching police to disperse the crowd on State Street amid concerns that hundreds of people began climbing on a construction site.
Police voiced concerns over the scanner traffic that the horziontal beams holding up the structure on which the crowd perched had begun to crack.
There were also scanner reports of a crowd of people outside the Jimmy John's on State Street throwing bottles at officers.
