YouTube Video of Madison, Wisconsin Rally, March 12, 2001

Saturday, March 12, 2011 saw the biggest crowds yet descend on Madison, Wisconsin to support labor unions and oppose Governor Scott Walker's bill stripping members of public-sector unions of their collective bargaining rights. Crowd size estimates ranged from 100,000 to 200,000, but you can see the size of the massive crowd yourself by watching this YouTube video of the rally.


Here's a link to another crowd size estimate which seems right to me. The author, a scientist at the UW Madison Geology Museum, appears to have researched relevant literature on crowd size estimating and shows his math.