I compile a balanced panel of 2,174 publicly traded firms and track their board structure from 1999 to 2006. I detail how boards responded to new regulation (introduced in 2002 and enacted in 2003) that required boards of firms traded on the NYSE and NASDAQ exchanges to have a strict majority of outside directors. I examine how non-compliant boards moved into compliance and compare their behavior to compliant firms. Non-compliant firms increased independence, but did not increase board size during the regulatory adjustment period. In addition to offering a detailed look at the data, I create a stylized model of board composition and size and suggest how the responses of non-compliant firms to the exogenous regulatory shock can be used to estimate the curvature of a board "production function."